RESEARCH ARTICLE
Have beliefs in conspiracy theories increased
over time?
Joseph UscinskiID
1☯
*, Adam Enders2☯
, Casey Klofstad1☯
, Michelle SeeligID
3‡
,
Hugo Drochon4‡
, Kamal PremaratneID
5‡
, Manohar Murthi5‡
1 Department of Political Science, University of Miami, Coral Gables, FL, United States of America,
2 Department of Political Science, University of Louisville, Louisville, KY, United States of America,
3 Department of Cinema and Interactive Media, University of Miami, Coral Gables, FL, United States of
America, 4 School of Politics and International Relations, University of Nottingham, Nottingham, United
Kingdom, 5 Department of Electrical and Computer Engineering, University of Miami, Coral Gables, FL,
United States of America
☯ These authors contributed equally to this work.
‡ These authors also contributed equally to this work
* uscinski@miami.edu
Abstract
The public is convinced that beliefs in conspiracy theories are increasing, and many scholars,
journalists, and policymakers agree. Given the associations between conspiracy theories
and many non-normative tendencies, lawmakers have called for policies to address
these increases. However, little evidence has been provided to demonstrate that beliefs in
conspiracy theories have, in fact, increased over time. We address this evidentiary gap.
Study 1 investigates change in the proportion of Americans believing 46 conspiracy theories;
our observations in some instances span half a century. Study 2 examines change in
the proportion of individuals across six European countries believing six conspiracy theories.
Study 3 traces beliefs about which groups are conspiring against “us,” while Study 4
tracks generalized conspiracy thinking in the U.S. from 2012 to 2021. In no instance do we
observe systematic evidence for an increase in conspiracism, however operationalized. We
discuss the theoretical and policy implications of our findings.
Introduction
An emerging research program focused on conspiracy theories has produced a robust literature
on the causes and consequences of beliefs in those theories [1]. Numerous studies find
that conspiracy theory beliefs are positively associated with non-normative behaviors, including
criminal acts [2], and negatively associated with pro-social behaviors, such as vaccination
[3,4]. Recent events, such as the election of Donald Trump, the U.S. Capitol riot, and several
conspiracy theory-inspired mass shootings, have prompted widespread concern from scholars,
journalists, and the mass public about increases in mass conspiracism.
As for the mass public, 73% of Americans believe that conspiracy theories are currently
“out of control” and 59% agree that people are more likely to believe conspiracy theories “compared
to 25 years ago” [5,6]. Approximately 77% of Americans believe that social media and
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OPEN ACCESS
Citation: Uscinski J, Enders A, Klofstad C, Seelig
M, Drochon H, Premaratne K, et al. (2022) Have
beliefs in conspiracy theories increased over time?
PLoS ONE 17(7): e0270429. https://doi.org/
10.1371/journal.pone.0270429
Editor: Sean Eric Richey, Georgia State University,
UNITED STATES
Received: February 4, 2022
Accepted: June 8, 2022
Published: July 20, 2022
Copyright: © 2022 Uscinski et al. This is an open
access article distributed under the terms of the
Creative Commons Attribution License, which
permits unrestricted use, distribution, and
reproduction in any medium, provided the original
author and source are credited.
Data Availability Statement: Data files are
available on OSFHOME, the Open Science
Framework: https://osf.io/kys8z/.
Funding: National Science Foundation Grant
#2123635 paid for effort by JU, CK, MS, KP, and
MM’s efforts. URL: https://www.nsf.gov/ Portions
of the data used in this study was funded by the
Leverhulme Trust. Project title: Conspiracy and
Democracy URL: https://www.leverhulme.ac.uk/
former-schemes/conspiracy-and-democracy The
funders had no role in study design, data collection
the Internet are responsible for these increases [7]. Many scholars agree, and view conspiracy
theories as indicative of a modern “crisis,” similarly citing new communication technologies as
a primary cause [8,9]. Journalists contend that we are living in the “golden age” of conspiracy
theorizing, a “post-truth” era in which conspiracy theories “have never spread this swiftly” nor
“lodged this deeply in the American psyche” [10–12]. Similar sentiments are frequently
expressed in reporting outside the U.S. as well [13]. Government officials worldwide have
responded with policy proposals to address, as one U.S. Congressperson put it, the “stupendous
rise in the popularity and prevalence” of conspiracy theories [14]. If beliefs in conspiracy
theories are increasing the way popular intuitions, scholars, media narratives, and politicians
suggest, there is ample reason for alarm.
Despite a litany of claims from different knowledge producers and consumers, little systematic
evidence has been provided to show that beliefs in conspiracy theories have increased over
time. While we observe troublingly high percentages of people believing in conspiracy theories
on cross-sectional polls and limitless conspiracy theory-related Internet content and social
media activity, we argue that these observations cannot, alone, be taken as evidence of
increases in conspiracism. Single cross-sectional polls cannot speak to temporal change, social
media activity cannot shed light on beliefs prior to the proliferation of Internet access, and
Internet content and social media interactions bear only a vague resemblance to mass beliefs
[15]. However, looking to repeated opinion polls measuring conspiratorial beliefs over time,
especially those taken before social media, does constitute one strategy for assessing change.
Unfortunately, such efforts have been quite limited.
This is to the detriment of the study of conspiracism beyond questions about the veracity of
the people’s and politicians’ perceptions of change over time. First, studies of conspiracism
over time can shed important light on the impact of situational factors and other idiosyncrasies
on beliefs, providing researchers with a unique window into the dynamics and antecedents of
conspiracy theory beliefs. Second, data such as this can also aid researchers in understanding
the comparative dynamics of conspiracism across socio-political contexts, such as types of government.
Third, the presence or absence of trends in conspiracism can speak directly to recent
concerns about the potential role of social media in fueling conspiracy theory beliefs, which
has tangible implications for policy regarding online content moderation and access. More
generally, concerns about changes to the socio-political landscape that implicate conspiracy
theories––from polarization to democratic backsliding––can only be fully tested with data
tracking changes in conspiracy theory beliefs over time.
Given the lack of confirmatory evidence and the stakes involved, it is imperative that the
popular narrative—that beliefs in conspiracy theories have increased over time—be treated as a
falsifiable hypothesis, and then carefully and extensively tested with appropriate over time data
measuring beliefs. We therefore, examine time series data of varying lengths from several
countries, including a wide variety of conspiracy theory beliefs and other operationalizations
of conspiracism. Study 1 investigates over time change in the proportion of Americans believing
46 individual conspiracy theories and four pieces of misinformation, with time spans ranging
from seven months (e.g., COVID-19 conspiracy theories) to 55 years (e.g., Kennedy
assassination conspiracy theories). Study 2 examines beliefs in six specific conspiracy theories
across six European countries between 2016 and 2018. Moving away from beliefs in specific
conspiracy theories and toward more general operationalizations of conspiracism in the U.S.,
Study 3 tracks changes in perceptions about which social and political groups are conspiring,
and Study 4 analyzes trends in generalized conspiracy thinking from 2012 to2021. Across all
studies, we fail to observe compelling evidence that either specific conspiracy theory beliefs or
general forms of conspiracism have increased.
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and analysis, decision to publish, or preparation of
the manuscript.
Competing interests: The authors have declared
that no competing interests exist.
Ethics
All polls fielded by the authors included only adults 18 years and older. Affirmative consent
was provided by respondents by checking a box via computer screen before beginning the survey.
Details of institutional review board approval for all author-fielded surveys is included in
the SI.
Study 1: Beliefs in specific conspiracy theories
A conspiracy theory is an explanation of past, present, or future events or circumstances that
cites as the primary cause a small group of powerful people working in secret, for their own
benefit, against the common good, and in a way that undermines bedrock ground rules against
the widespread use of force and fraud [16]. Furthermore, conspiracy theories have not been
judged as likely accurate by the appropriate epistemological bodies using publicly available evidence
[17]. A conspiracy theory belief is one’s acceptance that a specific conspiracy theory is
(likely) true. Our first investigation utilizes more than 40 conspiracy theories to test the simplest
version of the hypothesis that conspiracy theory beliefs are increasing:
H1: The proportion of people believing specific conspiracy theories in the U.S. has increased
over time.
Because we test this hypothesis using numerous conspiracy theories, each conspiracy theory
constitutes a unique test. We would reject the null hypothesis (that the proportions believing
specific conspiracy theories in the U.S. have not increased over time) in favor of H1 if 1) a
majority of the conspiracy theory beliefs we examine show evidence of significant increase
from Time1 to Time2, or, if 2) the increases we observe are larger in magnitude than any
decreases we observe. We focus on increases in positive expressions of belief (i.e., professing to
agree with, or believe, a conspiracy theory) rather than on changes in levels of disagreement or
of being unsure. Our hypothesis, and the popular claims it is based on, speak to increases in
belief, rather than changes in the intensity of non-belief.
To test H1, we re-poll the U.S. public about their beliefs in dozens of conspiracy theories,
repeating the exact question wordings used on national polls fielded between 1966 and 2020.
While such a research design—comparing previous survey findings to more recent ones—
offers a straightforward approach, many specifics about what an appropriate test entails are
absent from the popular claims. This lack of specificity has made it difficult to falsify such
claims; it also leaves us with little guidance as to the proper length between T1 and T2, or to
which conspiracy theories should be examined. We address these details in turn.
First, whether made by scholars, journalists, or policymakers, claims about increases in conspiracy
theory beliefs often lack specificity regarding the rate or absolute levels of change in
conspiracy beliefs. Some accounts suggest that increases should be swift, easily detectable, and
on-going, with people venturing down “conspiracy-fueled rabbit holes” on social media, thus
finding “themselves believing in elaborate conspiracy theories about Bill Gates, 5G wireless
technology, vaccines and masks,” and then, “within days, they begin to believe that President
Donald Trump is waging a secret war to save trafficked children from a cabal of Satanworshipping
baby eaters” [18]. Other accounts are less specific, suggesting only that we have
entered the “golden age” of conspiracy theorizing [19].
Anecdotes aside, one may wonder how far apart T1 and T2 should be. Do conspiracy beliefs
increase linearly or nonlinearly? By the week? The year? Should we expect greater increases
over a 50-year period than a single year? Should increases only be found during the social
media era? Much like the journalistic accounts, previous scholarship also fails to offer clear
guidance on these questions, leaving theorizing about the form that a growth (or decay)
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function might take as either post-hoc or case specific. We remain agnostic to questions
regarding the rate of change, with H1 positing only that the levels of conspiracy theory beliefs at
T2 are significantly greater than those at T1. Therefore, we test H1 comprehensively, intentionally
altering assumptions and details. Specifically, we employ 1) comparisons ranging from
seven months to 55 years, and 2) conspiracy theories that vary both in age and in the presumed
salience of the events and circumstances they address. The conspiracy theories we test range
from centuries (e.g., Rothschild family) or decades old (e.g., Pearl Harbor attack), to only a
year old (e.g., COVID-19). The length of time between our measurements provides ample
potential for growth to be detected, even at the shortest time length (seven months).
Second, claims about increases in conspiracy theory beliefs often fail to specify which conspiracy
theories they are referring to. Many accounts suggest that beliefs in all conspiracy theories
are increasing [10], implying that growth should be detectable for any conspiracy theory.
Furthermore, popular accounts rarely set limits on their claims by, for example, delineating
which, if any, conspiracy theories should not be expected to increase in popularity over time.
Researchers cannot examine every conspiracy theory because the universe of conspiracy theories
and versions thereof are constantly expanding and seemingly infinite. Given that an investigation
of beliefs in all or most conspiracy theories is impossible, we test H1 using a large
number of survey items spanning the five categories of conspiracy theories identified by Brotherton,
French, and Pickering [20]: government malfeasance (e.g., government assassinating
celebrities), extraterrestrial cover-up (e.g., government hiding alien contact), malevolent global
conspiracies (e.g., George Soros controlling the world), personal well-being (e.g., vaccines contain
tracking devices), and control of information (e.g., Jeffrey Epstein murdered as part of a
cover-up). Because this study is situated in the U.S. where partisan politics often inflames conspiracy
theory beliefs [21], we also include conspiracy theories involving partisan actors and
issues (e.g., Barack Obama faked his birth certificate). Casting this wide net ensures that our
results provide a comprehensive test of H1 and generalize to the broader universe of conspiracy
theories.
Despite taking these steps, we note three natural limitations to the scope of our study. First,
because we are interested in change between T1 and T2, our analyses are restricted to the universe
of conspiracy theories previously included on at least one national survey. Second, our
analyses must rely on previous measurements at the time they were taken, and not necessarily
when the conspiracy theories were initially developed or when the event or circumstance those
conspiracy theories address occurred. Third, an increase in conspiracism over time could
result in fewer conspiracy-minded individuals participating in polls, thereby providing a
downwardly biased estimate of conspiracy beliefs at T2. While Study 4, which examines the
predisposition toward conspiracy thinking over time and finds stability over the course of a
decade, seems to suggest that this is not an issue, we cannot fully rule out the possibility that it
is indeed an issue affecting our results. We begin by testing H1 with two critical cases that have
recently attracted significant attention: conspiracy theories regarding COVID-19 and QAnon.
We then further test H1 using 37 other conspiracy theories.
COVID-19 conspiracy theories
Throughout the pandemic, many scholars and journalists argued that COVID-19 conspiracy
theory beliefs were on the rise [22]. For this reason, COVID-19 conspiracy theories represent a
critical test of H1.
We polled on two COVID-19 conspiracy theories in the U.S. in March 2020 (Fig 1): “Coronavirus
was purposely created and released by powerful people as part of a conspiracy” and
“The threat of coronavirus has been exaggerated by political groups who want to damage
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President Trump.” Details about survey methodology and sample demographics appear in the
appendix. These two theories cover the basic contours of COVID-19 conspiracy theories in
the U.S. at the beginning of the pandemic [3]. In repeated polls, however, we observe no
increases in either belief (Fig 1). The theory that the coronavirus was “purposely created and
released” found support among 31% of Americans in March 2020, 27% in June 2020, and 29%
in May 2021. We note that the “lab leak hypothesis” attracted significant attention from policymakers
and journalists in the month leading up to our May 2021 survey, yet this does not
appear to have fueled increases in the belief that coronavirus was “purposely created and
released.” The theory that the coronavirus was exaggerated to “damage President Trump”
stood at 29% in March 2020, it was 28% in June 2020, and then increased (non-significantly)
to 31% in October 2020 (p = 0.086).
Table 1 (below) includes responses to beliefs in three additional pandemic-related conspiracy
theories polled in June 2020 and May 2021: “The coronavirus is being used to
force a dangerous and unnecessary vaccine on Americans,” “Bill Gates is behind the coronavirus
pandemic,” and “The coronavirus is being used to install tracking devices inside
our bodies.” All three decreased; the Bill Gates and tracking device theories significantly
decreased three and six points, respectively. We observe no evidence of increased beliefs
for these five COVID-19 conspiracy theories precisely when increases were most expected.
Our results are congruent with those produced by Romer & Jamieson [3], who find that
beliefs in three different COVID-19-related conspiracy theories were stable between
March and July 2020.
Fig 1. Beliefs in COVID-19 conspiracy theories in the U.S.
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We also examine changes in four pieces of COVID-19 misinformation often tied to conspiracy
theories (bottom, Table 1). The hydroxychloroquine item showed no change over
time, while beliefs regarding 5G and disinfectant decreased significantly (−4 and −6 points,
respectively). The only increase identified regarded the idea that the number of COVID-
19-related deaths was exaggerated (+7 points). Precisely during the timeframe in which these
beliefs were widely said to be spreading, we observe no evidence of over time growth in the
five COVID-19 conspiracy theory beliefs we queried; of the four pieces of misinformation we
polled on, only one showed evidence of increase.
QAnon belief and related conspiracy theories
Our second critical case involves QAnon. Numerous reports claimed that belief in QAnon was
“spreading,” “growing,” and riding the pandemic “to new heights” [18,23,24]. QAnon adherents
believe that a government insider sent them secret messages about President Trump’s battle
against the sex-trafficking deep state [25]. Beyond this canonical belief, QAnon supporters
believe heterogenous collections of conspiracy theories regarding the deep state, Satanic cults,
and sex abuse [26], many of which existed long before QAnon’s emergence in 2017 [27] and
find support among a more extensive base than the typically small number of Americans who
express belief in QAnon, specifically [28]. We, therefore, gauge belief in QAnon using a variety
of survey items in Table 2.
The first, and most direct, asks “Are you a believer in QANON?”, to which five percent of
respondents replied “yes,” in August 2019. We re-polled this question in May 2021, observing
a nonsignificant increase of one point. We then examined beliefs in conspiracy theories often
associated with QAnon including those regarding the “deep state,” elite sex traffickers, and Jeffrey
Epstein. Consistent with other polls [e.g., 26], these theories garner support from between
34 and 50 percent of Americans, reaching far outside the six percent who identify as a “believer
in QAnon.” While the baseline levels of belief in these theories are normatively troubling, in
no instance do we observe evidence of significant over time increases.
Finally, we asked respondents to rate the “QAnon movement” on a feeling thermometer
ranging from 0 (very “cold,” negative feelings) to 100 (very “warm,” positive feelings). If belief
in or support for QAnon were increasing, we would expect to observe increases in the average
rating assigned to it. However, we find the opposite: in July 2019, the average rating was 21
and by May 2021, the average rating decreased to 16. In total, belief in and support for QAnon,
Table 1. Change in COVID-19 conspiracy beliefs and misinformation between June 2020 and May 2021.
Question wording Percent,
June 2020
Percent
May 2021
Diff. p-value for
difference
Conspiracy theories
1. The coronavirus is being used to force a dangerous and unnecessary vaccine on Americans. 25 24 −1 0.541
2. Bill Gates is behind the coronavirus pandemic. 13 10 −3 0.012
3. The coronavirus is being used to install tracking devices inside our bodies. 18 12 −6 <0.001
Misinformation
1. The number of deaths related to the coronavirus has been exaggerated. 29 36 +7 <0.001
2. Hydroxychloroquine can prevent or cure COVID-19. 18 18 0 >0.999
3. 5G cell phone technology is responsible for the spread of the coronavirus. 11 7 −4 <0.001
4. Putting disinfectant into your body can prevent or cure COVID-19. 12 6 −6 <0.001
Note: P-value corresponds to two-tailed difference in proportions test. All polls are of U.S. adults. Proportions correspond to those saying they “agree” or “strongly
agree” with each sentiment. June 2020 and May 2021 polls were both online, opt-in.
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as well as beliefs in ideas that the QAnon movement broadly adopted, remained stable
throughout the pandemic and 2020 election cycle, precisely when the QAnon movement was
widely perceived to be increasing in size.
Other conspiracy theories
Moving beyond COVID-19 and QAnon, our analysis continued with a search of the Roper
Center for Public Opinion database––the most comprehensive repository of publicly available
polling data in the U.S.—for survey items about conspiracy theories that had been administered
to national samples in the past. Our search identified only 10 of such items prior to 2010,
reflecting the fact that attention to conspiracy theories (especially that involving national polling)
is largely concentrated in the last decade. Still, the past polls we identified address a range
of topics: the assassinations of President Kennedy, Robert Kennedy, and Martin Luther King
Jr., as well as the moon landing, UFOs, AIDS, Pearl Harbor, O.J. Simpson, the Reagan Administration,
and the police. We further expanded our search by utilizing items drawn from prominent
studies spanning the last decade [29,30].
Our search identified a total of 37 items (polled between 1966–2020) addressing conspiracy
theories that vary in who they accuse, which groups in society are/were likely to believe them,
the types of events or circumstances they seek to explain, how long they have existed, how
widely believed they are/were, and their relative salience. To enable precise comparisons, we
re-polled each of the 37 items, retaining the exact question wording and response options used
in previous surveys. In all cases, T2 polls were conducted online using an opt-in, quota-based
sampling procedure; T1 polls were sampled using a mixture of random sampling and opt-in
procedures and fielded over the telephone (n = 10 with a live interviewer, n = 6 automated),
in-person (n = 2), and online (n = 56). We also note that some surveys in the past were
restricted to registered voters; in those instances, we also restrict our analysis of the follow-up
survey to registered voters. The appendix contains detailed information about all items and
polls.
In Table 3, we observe little support for H1. Of the 37 conspiracy theory beliefs examined,
only six show a significant over time increase, ranging from four to 10 percentage points in
magnitude. Of the remaining 31, 16 show no significant change and 15 show a statistically
Table 2. Change in QAnon and QAnon-related beliefs over time.
Question wording Time 1 Time 2 Diff. p-value for
difference
Percentage 1 Percentage 2
1. Are you a believer in QANON? (Yes/No) 5
(08/2019)
6
(05/2021)
+1 0.205
2. There is a “deep state” embedded in the government that operates in secret and without oversight. 43
(03/2020)
44
(05/2021)
+1 0.521
3. Elites, from government and Hollywood, are engaged in a massive child sex trafficking racket. 35
(10/2020)
34
(05/2021)
−1 0.504
4. Jeffrey Epstein, the billionaire accused of running an elite sex trafficking ring, was murdered to cover-up
the activities of his criminal network.
50
(03/2020)
48
(05/2021)
−2 0.203
Average 1 Average 2
5. QAnon movement (feeling thermometer, 0–100) 21
(07/2019)
16
(05/2021)
−5 <0.001
Note: P-value corresponds to two-tailed difference in proportions test. All polls are of U.S. adults. Proportions correspond to those saying they “agree” or “strongly
agree” with each sentiment. All polls were both online, opt-in.
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Table 3. Change in 37 additional conspiracy beliefs over time.
Question wording Percentage 1
(Time 1)
Percentage 2
(Time 2)
Diff. p-value for
difference
1. Humans have made contact with aliens and this fact has been deliberately hidden from the public. 23 (07/2019) 33 (03/2020) +10 <0.001
2. Do you think the U.S. government has engaged in the assassination of entertainers who have tried to spread a
counterculture message they didn’t like, such as John Lennon, Kurt Cobain, Tupac Shakur, and others, or not?ab
12 (09/2013) 20 (05/2021) +8 <0.001
3. Billionaire George Soros is behind a hidden plot to destabilize the American government, take control of the
media, and put the world under his control.
19 (10/2011) 26 (05/2021) +7 <0.001
4. Do you think one man was responsible for the assassination of President Kennedy, or do you think there were
others involved?b
50 (12/1966) 56 (05/2021) +6 <0.001
5. Do you believe that the pharmaceutical industry is in league with the medical industry to "invent" new diseases in
order to make money, or not? ab
15 (03/2013) 20 (05/2021) +5 <0.001
6. Thinking about space exploration, do you think the government staged and faked the Apollo moon landings, or
don’t you feel that way?b
6 (07/1995) 10 (05/2021) +4 <0.001
7. Do you believe media or the government adds secret mind-controlling technology to television broadcast signals,
or not? ab
15 (03/2013) 17 (05/2021) +2 0.132
8. Do you believe the government adds fluoride to our water supply, not for dental health reasons, but for other, more
sinister reasons, or not? ab
9 (03/2013) 11 (05/2021) +2 0.067
9. Do you think the government is keeping information from the public that shows U.F.O.’s (Unidentified Flying
Objects) are real or that aliens have visited the Earth?b
49 (06/1996) 50 (05/2021) +1 0.637
10. Hillary Clinton conspired to provide Russia with access to nuclear materials. 28 (03/2020) 29 (04/2021) +1 0.481
11. The U.S. government is mandating the switch to compact fluorescent light bulbs because such lights make people
more obedient and easier to control.
11 (10/2011) 12 (05/2021) +1 0.325
12. Health officials know that cell phones cause cancer but are doing nothing to stop it because large corporations
won’t let them.
20 (09/2013) 20 (05/2021) 0 >0.999
13. Certain U.S. government officials planned the attacks of September 11, 2001, because they wanted the United
States to go to war in the Middle East.
19 (10/2011) 19 (05/2021) 0 >0.999
14. Regardless of who is officially in charge of governments and other organizations, there is a single group of people
who secretly control events and rule the world together.
35 (03/2020) 35 (10/2020) 0 >0.999
15. The number of Jews killed by the Nazis during World War II has been exaggerated on purpose. 15 (03/2020) 15 (10/2020) 0 >0.999
16. Climate change is a hoax perpetrated by corrupt scientists and politicians. 19 (07/2019) 19 (10/2020) 0 >0.999
17. Barack Obama faked his citizenship to become president. 20 (03/2020) 19 (05/2021) −1 0.422
18. Do you completely agree, mostly agree, mostly disagree, or completely disagree that AIDS is a form of systematic
destruction of minorities like blacks and Hispanics?b
16 (11/1995) 15 (05/2021) −1 0.416
19. The dangers of vaccines are being hidden by the medical establishment. 30 (03/2020) 29 (05/2021) −1 0.486
20. The Food and Drug Administration is deliberately preventing the public from getting natural cures for cancer and
other diseases because of pressure from drug companies.
37 (09/2013) 35 (05/2021) −2 0.235
21. The one percent (1%) of the richest people in the U.S. control the government and the economy for their own
benefit.
55 (03/2020) 52 (05/2021) −3 0.056
22. A powerful family, the Rothschilds, through their wealth, controls governments, wars, and many countries’
economies.
29 (03/2020) 26 (05/2021) −3 0.033
23. The AIDS virus was created and spread around the world on purpose by a secret organization. 22 (03/2020) 19 (06/2020) −3 0.054
24. The dangers of 5G cellphone technology are being covered up. 26 (03/2020) 23 (10/2020) −3 0.027
25. Do you feel that the Assassination of Senator Robert Kennedy was the act of one individual or part of a larger
conspiracy?b
48 (03/1981) 43 (05/2021) −5 0.009
26. The dangers of genetically-modified foods are being hidden from the public. 45 (03/2020) 40 (05/2021) −5 0.001
27. School shootings, like those at Sandy Hook, CT and Parkland, FL are false flag attacks perpetrated by the
government.
17 (03/2020) 12 (10/2020) −5 <0.001
28. Do you believe that Osama bin Laden is dead, or do you think he is still alive?b
11 (06/2011) 5 (05/2021) −6 <0.001
29. Donald Trump colluded with Russia to rig the 2016 presidential election. 41 (07/2019) 34 (05/2021) −7 <0.001
30. Some people are hiding the truth about the December 14, 2012 school shooting at Sandy Hook Elementary in
order to advance a political agenda.ab
25 (04/2013) 16 (05/2021) −9 <0.001
31. Some people have argued that President Franklin D. Roosevelt knew about Japanese plans to bomb Pearl Harbor
but did nothing about it because he wanted an excuse to involve the U.S. (United States) on the side of the allies in the
war.b
31 (11/1991) 19 (05/2021) −12 <0.001
(Continued)
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significant decrease. Significant decreases range in magnitude from three to 31 points. The
average change across all conspiracy beliefs is −3.84 points. Altogether, the number of conspiracy
theory beliefs that increased—six out of 37—is outweighed by the 31 conspiracy theories
showing either no change or a significant decrease.
To account for these findings, one might wonder whether the conspiracy theories that fail
to show an increase, or that show a decrease, are somehow systematically different from those
that show an increase. Examining the beliefs that increased in Table 3 reveals timespans, subject
areas, baseline levels of belief, and question wording types similar to those that decreased
or remained stable. For example, the largest decrease (31 points) regards beliefs about the 1980
release of the hostages from Iran, which were initially polled in 1991. On the one hand, it
could be that this conspiracy theory lost popularity due to its age. But an attempt to discount
this item from our analysis for this reason would require significant post-hoc theorizing, especially
given that some of the largest increases we observe are among conspiracy theories that
also address similarly dated topics (JKF, aliens, John Lennon, and George Soros) that were also
initially polled on many years ago. The salience of a conspiracy theory likely has something to
do with its age or the age of the object it addresses, but salience is also idiosyncratic and the
product of numerous factors. The “fluorescent lightbulb” conspiracy theory (Table 3, #11),
which did not increase over time (p = 0.325), might shed some light on the potential importance
of salience. Because this theory was concocted by researchers [30], it––to our knowledge––never
spread among the public and its salience was therefore held constant. Hence,
when the salience of, and information about, a conspiracy theory and the topic it addresses are
stable over time (there never was any organic public attention paid to this theory), beliefs
appear to remain stable over time as well.
That said, we took additional steps to investigate whether there is a relationship between
the “age” of a conspiracy theory and belief in it. We first computed the correlation between a)
the difference in proportion of believers listed in Table 1 (column 4) and b) the time (in years)
between T1 and T2. The correlation is –0.32 (p = 0.010), signifying that the longer a conspiracy
theory has been around, the less support it garners. Second, we examined whether there was
any relationship between the time a given conspiracy theory belief was first surveyed in our
data and the proportion of individuals supporting it at that time––perhaps individual conspiracy
theory beliefs are not increasing over time, but rather new conspiracy theories are
Table 3. (Continued)
Question wording Percentage 1
(Time 1)
Percentage 2
(Time 2)
Diff. p-value for
difference
32. Republicans won the presidential elections in 2016, 2004, and 2000 by stealing them. 27 (03/2020) 15 (05/2021) −12 <0.001
33. Do you believe global warming is a hoax, or not?b
37 (03/2013) 19 (05/2021) −18 <0.001
34. Do you think there was a police conspiracy to frame O.J. Simpson or not?b
34 (10/1995) 11 (05/2021) −23 <0.001
35. Do you feel that the Assassination of Martin Luther King was the act of one individual or part of a larger
conspiracy?b
59 (03/1981) 33 (05/2021) −26 <0.001
36. Do you think there is, or is not, a national conspiracy to kill police?b
44 (11/1970) 16 (05/2021) −28 <0.001
37. Do you think that the Reagan campaign made a deal with the Iranians to hold the American hostages in Iran until
after the 1980 presidential election or not?b
43 (07/1991) 12 (05/2021) −31 <0.001
Note: P-value corresponds to two-tailed difference in proportions test. All polls are of U.S. adults. Where response options are not dichotomous (e.g., yes/no, believe/
don’t believe), the proportion expressing belief is those who “agree” or “strongly agree” with a sentiment.
a
Registered voters only.
b
Explicit “don’t know” or “no opinion” option provided; otherwise respondents could opt-out of answering or select “neither agree nor disagree”.
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garnering more initial support today than conspiracy theories did in the past. Here, too, we
find no support for such a notion; instead, there is a negative correlation (r = –0.44, p = 0.006)
between the date each conspiracy theory was first polled and level of support. Thus, it seems
that conspiracy theories tend to lose, rather than gain, believers over time and that “newer”
conspiracy theories are not attracting more believers than did conspiracy theories in the past.
These observations cut against the popular claims upon which H1 is based. That said, we suspect
that individual conspiracy theories respond to different forces over time, attracting more
or fewer adherents for idiosyncratic reasons, just like many other topics of public opinion do.
We also consider the potential role of “don’t know” and “no opinion” responses, especially as
they pertain to observed changes in “older” conspiracy theory beliefs; this analysis, which is
presented in the appendix, does not reveal an effect in “don’t know” responses.
One might additionally wonder if survey methodologies and modes (e.g., phone versus
computerized surveys) are affecting our results. First, we note that our survey samples were
constructed to be representative of the U.S. adult population according to the most recent census
estimates; this information is presented in the appendix. Second, we suspect that changes
in polling methods would work in favor of H1, rather than against it, given that surveys guided
by a live interviewer––the norm for most polls more than 10 years old––would be more likely
to trigger social desirability bias, thereby depressing stated conspiracy beliefs, compared to
computerized polls where no interviewer is present. However, we observe no patterns suggesting
that our findings are systematically impacted by polling method. Indeed, even when our
comparisons employ the same sampling method and administration mode at T1 and T2, we
observe more decreases than increases. In the appendix, we further interrogate the potential
impact of survey mode and questionnaire design; in no instance do we observe patterns suggesting
that mode or design features are confounding inferences.
Given the frequency of claims about contemporary America entering a “golden age” of conspiracy
theories [10,19,31], we expected to find near-universal support for H1, regardless of the
specific conspiracy theories or the timeframes used in our comparisons. However, our analyses
failed to produce consistent evidence of such. Out of 46 total conspiracy theories and related
misinformation examined in Study 1, we found only seven with significant increases, but 22
with no significant change and 17 with significant decreases. Moreover, the conspiracy theories
that have recently attracted the most concern over their supposed growth (those regarding
COVID-19, QAnon, and vaccines) do not appear to be growing in popularity.
Study 2: Conspiracy theory beliefs across cultures
To examine whether the findings outlined in Study 1 are confined to the U.S., we now test our
central hypothesis cross-nationally. In partnership with YouGov, we polled beliefs about six
conspiracy theories across six European countries in both 2016 and 2018. Our reconfigured
hypothesis is as follows:
H2: The proportion of people believing specific conspiracy theories in Germany, Great Britain,
Italy, Poland, Portugal, and Sweden has increased over time.
These countries were chosen because they vary in gross domestic product, population,
income inequality, political systems, and location within Europe (north/south, east/west), all
of which may impact belief in conspiracy theories. We leverage cross-national variability to
provide not only more, but potentially different, tests of the central hypothesis.
The surveys utilized here meet the specifications laid out in Study 1, asking conspiracy theory
questions a) the same way to b) national samples c) at least twice (in 2016 and again 2018).
These surveys also provide an adequate timeframe for detecting growth (two years), as well as
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a range of conspiracy theories spanning the five categories identified by Brotherton, French,
and Pickering [20]. Respondents were asked to select which of the following “statements,” if
any, they believe (labels in parentheses):
1. Humans have made contact with aliens and this fact has been deliberately hidden from the
public. (Alien Contact)
2. The AIDS virus was created and spread around the world on purpose by a secret group or
organisation. (AIDS Virus)
3. Regardless of who is officially in charge of governments and other organisations, there is a
single group of people who secretly control events and rule the world together. (Control
World)
4. The official account of the Nazi Holocaust is a lie and the number of Jews killed by the
Nazis during World War II has been exaggerated on purpose. (Holocaust Denial; excluded
in German sample)
5. The idea of man-made global warming is a hoax that was invented to deceive people.
(Global Warming)
6. The Government is deliberately hiding the truth about how many immigrants really live in
this country. (Hide Immigrants)
Fig 2 shows the proportion of respondents selecting each conspiracy theory, in each country,
by year. Out of the 35 comparisons presented, the proportion of believers significantly
increased over time in only one: Holocaust denial in Sweden increased from 1% to 3% of the
population, (p = 0.016). By contrast, we observe significant over time decreases in seven of the
comparisons. This leaves 27 of the 35 total cases with no statistically significant change.
These findings align with those of Study 1––most change is not significant and, of the significant
changes we observe, decreases outnumber increases. Because we examine only a small
number of conspiracy beliefs across six countries, we cannot preclude the possibility of
increases in other conspiracy beliefs, or in other countries. Therefore, while we fail to find supportive
evidence during a time and in contexts where growth was widely expected [32], we recommend
that future studies examine trends in more countries with more conspiracy theories.
Study 3: Beliefs about which groups are conspiring
In our third study, we transition from beliefs in specific conspiracy theories to perceptions
about which groups are likely to be conspirators. Our third hypothesis is as follows:
H3: The number of groups Americans believe are conspiring has increased over time.
While we are agnostic as to whether it is normatively worse for people to believe that multiple
groups, as opposed to one group, are actively conspiring against them, this constitutes an
ancillary test of the general hypothesis: even though the proportion of individuals expressing
belief in specific conspiracy theories appears largely stagnant, the number of groups and institutions
that people believe are behind those supposed conspiracies could be increasing.
To test this possibility, we asked respondents in four surveys fielded in October 2012,
2016, 2018, and 2020 which of several groups are “likely to work in secret against the rest
of us?” Respondents could choose one or more of nine groups: “corporations and the
rich,” “Republicans or other conservative groups,” “Democrats or other liberal groups,”
“Communists and Socialists,” “the government,” “foreign countries,” “international organizations
(e.g., United Nations, International Monetary Fund, World Bank),” “the
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Freemasons or some other fraternal group,” and “labor unions.” Respondents could also
select “none of the above,” or choose not to select any of the options, which we also classified
as “none of the above.” Fig 3 plots the proportion of respondents selecting each
option, by year/survey.
Across the nine years, we observe average decreases for three groups (corporations, international
organizations, and unions) and average increases for the six remaining groups, all of
which are significant (p<0.05). That said, the decreases are larger than the increases: the
Fig 2. Proportion of adults across 6 European countries who express agreement with each conspiratorial sentiment over time.
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average change in proportion across all nine groups of conspirators is –0.13. This is further
reflected in an examination of the average count of conspirators that respondents selected: in
2012 respondents selected 2.56 groups, on average, and 2.70 groups in 2020. This difference is
not statistically significant at conventional levels (p = 0.09). In sum, while fears about particular
conspirators ebb and flow over time, we do not observe an average increase in the number of
conspirators that people are worried about. Moreover, decreases in the proportion of individuals
expressing worry about various conspirators outweigh the observed increases.
Fig 3. Proportion of U.S. adults who beliefs that each group is “likely to work in secret against the rest of us” over time.
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Study 4: Conspiracy thinking
Finally, to answer perhaps the most important question regarding the role of conspiracy theories
in contemporary culture—have people become more conspiracy-minded, in general, over
time?—we examine temporal trends in the general predisposition to interpret events and circumstances
as the product of real conspiracies [20], conspiracy thinking. This analysis, like
Study 3, is particularly useful because it circumvents the trappings of individual conspiracy
theories (e.g., the details, supposed evidence, and salience) that can make generalization difficult.
Our fourth hypothesis follows:
H4: The average level of conspiracy thinking in the U.S. has increased over time.
We use eight surveys of U.S. adults fielded between October 2012––the earliest known measure
of generalized conspiracy thinking on a national survey––and May 2021 to test this
hypothesis. Each of our surveys measure conspiracy thinking the same way: the American
Conspiracy Thinking Scale (ACTS), first developed by Uscinski and Parent [33] and based on
items from McClosky & Chong [34]. This measure of conspiracy thinking has been previously
validated in numerous published studies and is strongly associated with beliefs in a wide range
of specific conspiracy theories [35–39]. Respondents are asked to react, using five-point scales
ranging from “strongly disagree” (1) to “strongly agree” (5), to each of the following four
items:
1. Even though we live in a democracy, a few people will always run things anyway.
2. The people who really “run” the country are not known to the voters.
3. Big events like wars, the recent recession, and the outcomes of elections are controlled by
small groups of people who are working in secret against the rest of us.
4. Much of our lives are being controlled by plots hatched in secret places.
Responses are averaged into a unidimensional and statistically reliable scale; for example,
Cronbach’s alpha ranges from 0.76–0.86 across the eight surveys (see appendix for
details). We examined the predictive validity of this measure using our most recent (May
2021) survey: respondents in the upper third of the ACTS express belief in more than three
times as many specific conspiracy theories than those falling in the lower third of the scale
(14 conspiracy theories versus four, respectively), even controlling for attitudinal and
demographic factors (see appendix). Predictive validity aside, we do not claim that conspiracy
thinking, as measured here, is the causal explanation for conspiracy theory beliefs;
instead, we merely propose that this measure is a proxy for the general propensity to believe
conspiracy theories.
Fig 4 plots the average of the ACTS for each survey, along with 95% confidence intervals
and an OLS fit line (β = –0.45, p = 0.269) to highlight trends (or the lack thereof). While we
observe an increase moving from 2012 to 2016 (p<0.001), it is substantively small at only
0.17 units on a five-point scale. All other time points display averages that are statistically
indistinguishable from 2012 levels (March 2020, p = 0.966; June 2020, p = 0.770) or statistically
lower than 2012 levels (2018, p = 0.026; 2019, p = 0.011; October 2020, p = 0.006; May
2021, p = 0.039). In short, we observe no average increase in conspiracy thinking over
time. This lack of an upward trend is disconfirmatory of the central hypothesis that conspiracism
has increased over time. We note, however, that average levels of conspiracy
thinking are potentially concerning, even if they are not increasing. Therefore, researchers
should continue investigating the scope of conspiracy thinking and develop strategies for
addressing it.
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Conclusion
Numerous cross-sectional polls show that large numbers of people believe conspiracy theories,
and online conspiracy theory content is plentiful. Perhaps because of this, many scholars, journalists,
and policymakers are concerned that conspiracism is increasing. However, little systematic
evidence demonstrating such increases has been produced. As one journalist at Vox
put it, “there’s no hard evidence that conspiracy theories are circulating more widely today
than ever before. But. . .it has certainly seemed like average Americans have bought into them
more and more” [40].
The lack of systematic evidence owes to the fact that conspiracy theories became the subject
of a sustained research program only around 2010. Regardless, claims about increases in conspiracy
theory beliefs must be both testable and falsifiable if they are to be taken seriously. Minimally,
hypothesized increases should be detectable using standard methods (such as, but not
limited to, polling). If such hypotheses cannot be substantiated with supportive evidence, they
should be appropriately qualified, refined to match the available evidence, or abandoned.
Across four studies––including four distinct operationalizations of conspiracism, temporal
comparisons spanning between seven months and 55 years, and tens of thousands of observations
from seven nations––we find only scant evidence that conspiracism, however operationalized,
has increased. Although beliefs in 13 out of 52 conspiracy theories significantly
increased over time (including those in both Study 1 and Study 2), these increases do not constitute
sufficient evidence against the null hypothesis. In fact, we identified more decreases
than increases, and the decreases were larger in magnitude than the increases. That only a
Fig 4. Average level of conspiracy thinking. Conspiracy thinking is measured with the ACTS (range 1–5), over time. Vertical
lines are 95% confidence intervals, horizontal line is OLS fit.
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quarter of the conspiracy theories we examined found more support over time––none of
which involve the COVID-19 pandemic or QAnon––contradicts common wisdom.
The baseline levels of conspiracism we observe are concerning and social scientists should
continue efforts at correcting them [e.g., 41]. By the same token, our finding that conspiracy
theory beliefs are generally not increasing has implications for public discourse. Claims that
beliefs in conspiracy theories are on the rise suggest that a new factor is to blame, or that a
meaningful change in an old factor has occurred. In this vein, social media has––perhaps erroneously––taken
much of the blame for supposed increases in conspiracy theory beliefs [CBS
7], which has implications for policies regarding content moderation and access.
However, we do not observe supporting evidence that beliefs in conspiracy theories or generalized
conspiracy thinking have increased during the Internet/social media era. Instead, our
findings comport with arguments that the Internet may be less hospitable to conspiracy theories
than is often assumed [42]. Our findings also comport with studies demonstrating that
online conspiracy theories, “infodemics,” and echo chambers may not be as widespread [43–
45] or influential as sometimes claimed [46], and are reflective of studies arguing that people
are not engaging with or sharing conspiracy theories online as much as sometimes assumed
[47–49]. Finally, the patterns we observe align with a broad literature on conspiracy theory
beliefs showing that people are unlikely to believe a conspiracy theory unless they are both 1)
already disposed to believe conspiracy theories generally, and 2) inclined towards the content
of that particular conspiracy theory or the source from which it emanates [39,50,51]. In other
words, online conspiracy theories might not persuade as much as reinforce existing views. Our
findings are more congruent with the latter process than the former.
That said, our investigation is not without limitations. We are limited to the conspiracy theories
polled on previously, and we cannot make claims about conspiracy theories we did not
investigate. Still, we expect that we are more likely to observe growth in the types of ideas that
researchers thought worthwhile to ask the public about than those they chose to ignore. We
acknowledge that the many claims about increases in conspiracism are often vague and could
mean numerous things. We have therefore tested several operationalizations of conspiracism
in our four studies, but future research should continue testing for increases in other ways as
well. We further acknowledge that no single study can poll in all political contexts. Some
beliefs not included in Study 2 could be increasing in the six European countries polled; moreover,
conspiracy theory beliefs could be increasing in some countries not accounted for here.
We note that most polling of conspiracy theory beliefs has taken place in the U.S. during the
last decade––efforts to comprehensively measure conspiracy theory beliefs with national polls
across the globe are only slowly emerging [e.g., 52]. More work outside the U.S. is needed to
test our central hypothesis more comprehensively.
We implore caution in making sweeping inferences from our findings. Our study should
not be used to make claims about, or to excuse the behavior of, political elites who weaponize
conspiracy theories. Moreover, trends in the coverage of conspiracy theories by news outlets
or in the rhetorical use of conspiracy theories by political elites fall outside the purview of our
investigation, as do the use of conspiracy theories by fake news purveyors, though we recommend
that researchers continue to consider these topics.
Questions regarding the growth in conspiracy theory beliefs are important, with far-reaching
normative and empirical implications for our understanding of political culture, free
speech, Internet regulation, and radicalization. That we observe little supportive evidence for
such growth, however operationalized, should give scholars, journalists, and policymakers
pause. This is not to dismiss the availability of conspiracy theories online, the large numbers of
people who believe in some conspiracy theories, or the potential consequences of those beliefs;
nor is it to preclude the possibility of increases in the future, in ways not tested here, or in
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other socio-political contexts. It may be that conspiracy theories have been a constant, but that
scholars, policymakers, and journalists are only recently beginning to pay appropriate attention
to them. Thus, our findings offer both good and bad news: good, in that conspiracy theory
beliefs are not increasing across the board; bad, in that conspiracy theories may be a more persistent
and ubiquitous feature of human society than is desirable. Scholars still have much to
discover about the psychology of conspiracy theory beliefs, as well as the role that elite communication
and the information environment play in promoting those beliefs. In the meantime,
we recommend caution in sounding alarms regarding the “golden age” of conspiracy theories
and the degeneration of society into a “post-truth” era.
Supporting information
S1 File. This file contains supplementary information about all polls and analyses.
(PDF)
Author Contributions
Conceptualization: Joseph Uscinski, Adam Enders, Casey Klofstad, Hugo Drochon, Kamal
Premaratne, Manohar Murthi.
Data curation: Joseph Uscinski, Adam Enders, Casey Klofstad, Michelle Seelig, Hugo Drochon,
Kamal Premaratne.
Funding acquisition: Joseph Uscinski, Casey Klofstad, Michelle Seelig, Kamal Premaratne,
Manohar Murthi.
Investigation: Joseph Uscinski, Adam Enders, Hugo Drochon.
Methodology: Joseph Uscinski, Adam Enders, Casey Klofstad.
Project administration: Joseph Uscinski, Casey Klofstad, Michelle Seelig, Hugo Drochon,
Manohar Murthi.
Resources: Joseph Uscinski.
Visualization: Adam Enders.
Writing – original draft: Joseph Uscinski, Adam Enders.
Writing – review & editing: Joseph Uscinski, Adam Enders, Casey Klofstad, Michelle Seelig,
Hugo Drochon, Kamal Premaratne, Manohar Murthi.
References
1. Butter M, Knight P, editors. Routledge Handbook of Conspriacy Theories. London: Routledge; 2020.
2. Jolley D, Mari S, Douglas KM. Consequences of conspiracy theories. In: Butter M, Knight P, editors.
Routledge Handbook of Conspiracy Theories. London: Routledge; 2020. p. 231–41.
3. Romer D, Jamieson KH. Conspiracy theories as barriers to controlling the spread of COVID-19 in the
US. Social Science & Medicine. 2020; 263(113356):1–8. https://doi.org/10.1016/j.socscimed.2020.
113356.
4. Goldberg ZJ, Richey S. Anti-Vaccination Beliefs and Unrelated Conspiracy Theories. World Affairs.
2020; 183(2):105–24. https://doi.org/10.1177/0043820020920554
5. Institute QUP. Quinnipiac University Poll, Question 29, 31118230.00028. In: Institute QUP, editor.
https://ropercentercornelledu/ipoll/study/31118230/questions#71e322a9-ef8b-4372-b37ba70b3bc3f06a.
Cornell University, Ithaca, NY: Roper Center for Public Opinion Research2021.
6. News C. CBS News Poll 31116742.00003, Question 4. In: Cornell University I, NY, editor. https://
ropercentercornelledu/ipoll/study/31116742/questions#eec11b78-0ed0-4b3c-bb13-0440e6770c7b.
Roper Center for Public Opinion Research2018.
PLOS ONE Conspiracy theories over time
PLOS ONE | https://doi.org/10.1371/journal.pone.0270429 July 20, 2022 17 / 19
7. News C. CBS News Poll, Question 6, 31116742.00005. In: Cornell University I, NY, editor. https://
ropercenter.cornell.edu/ipoll/study/31116742/questions#0af0a594-4a2e-4218-be7bd8b13928f0a0Roper
Center for Public Opinion Research; 2018.
8. Bak-Coleman JB, Alfano M, Barfuss W, Bergstrom CT, Centeno MA, Couzin ID, et al. Stewardship of
global collective behavior. Proceedings of the National Academy of Sciences. 2021; 118(27):
e2025764118. https://doi.org/10.1073/pnas.2025764118 PMID: 34155097
9. Dow BJ, Johnson AL, Wang CS, Whitson J, Menon T. The COVID-19 pandemic and the search for
structure: Social media and conspiracy theories. Social and Personality Psychology Compass. 2021.
https://doi.org/10.1111/spc3.12636 PMID: 34512798
10. Guilhot N, Moyn S. The Trump era is a golden age of conspiracy theories–on the right and left. The
Guardian [Internet]. 2020 5/20/2020. Available from: https://www.theguardian.com/commentisfree/
2020/feb/13/trump-era-conspiracy-theories-left-right.
11. Wang A. ‘Post-truth’ named 2016 word of the year by Oxford Dictionaries2016 5/24/2019. Available
from: https://www.washingtonpost.com/news/the-fix/wp/2016/11/16/post-truth-named-2016-word-of-
the-year-by-oxford-dictionaries/?utm_term=.c8caddde2e2a.
12. Jacobsen A. The United States of conspiracy: Why, more and more, Americans cling to crazy theories.
NYDailyNewscom [Internet]. 2011; (Sunday, August 7th). Available from: http://articles.nydailynews.
com/2011-08-07/news/29878465_1_conspiracy-theories-bavarian-illuminati-nefarious-business.
13. Strick K. QAnon, anti-vaxxers and the rise of dangerous conspiracy theories in the UK. Evening Standard
[Internet]. 2021 9/9/2021. Available from: https://www.standard.co.uk/news/uk/qanon-conspiracy-
theories-anti-vaxx-b918159.html.
14. Riggleman D. The spread of conspiracy theories like QAnon threatens our politics: GOP congressman.
USA Today [Internet]. 2020 5/24/2021. Available from: https://www.usatoday.com/story/opinion/2020/
11/14/conspiracy-theories-pose-threat-our-politics-and-civil-discourse-column/6241514002/.
15. Kim JW, Guess A, Nyhan B, Reifler J. The Distorting Prism of Social Media: How Self-Selection and
Exposure to Incivility Fuel Online Comment Toxicity. Journal of Communication. 2021. https://doi.org/
10.1093/joc/jqab034
16. Uscinski J. Conspiracy Theories: A Primer. New York, NY, USA: Rowman & Littlefield Publishers; 2020.
17. Levy N. Radically Socialized Knowledge and Conspiracy Theories. Episteme. 2007; 4(2):181–92.
https://doi.org/10.3366/epi.2007.4.2.181.
18. Collins B. How QAnon rode the pandemic to new heights—and fueled the viral anti-mask phenomenon.
NBC News [Internet]. 2020 8/15/2020. Available from: https://www.nbcnews.com/tech/tech-news/how-
qanon-rode-pandemic-new-heights-fueled-viral-anti-mask-n1236695.
19. Stanton Z. You’re Living in the Golden Age of Conspiracy Theories. POLITICO [Internet]. 2020 5/24/
2001. Available from: https://www.politico.com/news/magazine/2020/06/17/conspiracy-theories-
pandemic-trump-2020-election-coronavirus-326530.
20. Brotherton R, French CC, Pickering AD. Measuring Belief in Conspiracy Theories: The Generic Conspiracist
Beliefs Scale. Frontiers in Psychology. 2013; 4(279):1–15. Epub May 21, 2013. https://doi.org/
10.3389/fpsyg.2013.00279 PMID: 23734136
21. Miller JM, Saunders KL, Farhart CE. Conspiracy endorsement as motivated reasoning: The moderating
roles of political knowledge and trust. American Journal of Political Science. 2016; 60(4):824–44.
https://doi.org/10.1111/ajps.12234.
22. MacFarquhar N. Far-Right Extremists Move From ‘Stop the Steal’ to Stop the Vaccine. The New York
Times [Internet]. 2021 9/10/2021. Available from: https://www.nytimes.com/2021/03/26/us/far-right-
extremism-anti-vaccine.html?searchResultPosition=4.
23. Stelter B. QAnon is conspiratorial, dangerous, and growing. And we’re talking about it all wrong.
CNNcom [Internet]. 2020 6/3/2021. Available from: https://www.cnn.com/2020/08/14/media/qanon-
news-coverage/index.html.
24. Roose K. What Is QAnon, the Viral Pro-Trump Conspiracy Theory? The New York Times [Internet].
2021 8/5/2021. Available from: https://www.nytimes.com/article/what-is-qanon.html.
25. Suthaharan P, Reed EJ, Leptourgos P, Kenney JG, Uddenberg S, Mathys CD, et al. Paranoia and belief
updating during the COVID-19 crisis. Nature Human Behaviour. 2021. https://doi.org/10.1038/s41562-
021-01176-8 PMID: 34316049
26. Schaffner B. QAnon and Conspiracy Beliefs. https://www.isdglobal.org/wp-content/uploads/2020/10/
qanon-and-conspiracy-beliefs.pdf: ISD, 2020 Oct., 2020. Report No.
27. Rabo A. Conspiracy theory as occult cosmology in anthopology. In: Butter M, Knight P, editors. Routledge
Handbook of Conspiracy Theories. New York: Routledge; 2020. p. 81–93.
28. Enders A, Uscinski J, Klofstad C, Wuchty S, Seelig M, Funchion J, et al. Who Supports QAnon? A Case
Study in Political Extremism. Journal of Politics. 2022.
PLOS ONE Conspiracy theories over time
PLOS ONE | https://doi.org/10.1371/journal.pone.0270429 July 20, 2022 18 / 19
29. Democrats Jenson T. and Republicans differ on conspiracy theory beliefs. Public Policy Polling [Internet].
2013 August 3, 2013. Available from: http://www.publicpolicypolling.com/main/2013/04/
democrats-and-republicans-differ-on-conspiracy-theory-beliefs.html.
30. Oliver E, Wood T. Conspiracy Theories and the Paranoid Style (s) of Mass Opinion. American Journal
of Political Science. 2014; 58(4):952–66. https://doi.org/10.1111/ajps.12084.
31. Willingham A. How the pandemic and politics gave us a golden age of conspiracy theories. wwwcnncom
[Internet]. 2020 5/24/2021. Available from: https://www.cnn.com/2020/10/03/us/conspiracy-theories-
why-origins-pandemic-politics-trnd/index.html.
32. Economist T. Britain is becoming a land of conspiracy theorists. The Economist [Internet]. 2019 6/4/2021.
33. Uscinski J, Parent JM. American Conspiracy Theories. New York, NY, USA: Oxford University Press;
2014.
34. McClosky H, Chong D. Similarities and Differences between Left-Wing and Right-Wing Radicals. British
Journal of Political Science. 1985; 15(3):329–63. https://doi.org/10.1017/S0007123400004221.
35. Cassese EC, Farhart CE, Miller JM. Gender Differences in COVID-19 Conspiracy Theory Beliefs. Politics
& Gender. 2020; 16(4):1009–18. https://doi.org/10.1017/S1743923X20000409.
36. Miller JM. Psychological, Political, and Situational Factors Combine to Boost COVID-19 Conspiracy
Theory Beliefs. Canadian Journal of Political Science. 2020; 53(2):327–34. Epub 06/11. https://doi.org/
10.1017/S000842392000058X.
37. Klofstad CA, Uscinski JE, Connolly JM, West JP. What drives people to believe in Zika conspiracy theories?
Palgrave Communications. 2019; 5(1):36. https://doi.org/10.1057/s41599-019-0243-8
38. Stoler J, Enders AM, Klofstad CA, Uscinski JE. The Limits of Medical Trust in Mitigating COVID-19 Vaccine
Hesitancy among Black Americans. Journal of General Internal Medicine. 2021. https://doi.org/10.
1007/s11606-021-06743-3 PMID: 34021446
39. Enders A, Uscinski JE, Seelig MI, Klofstad CA, Wuchty S, Funchion JR, et al. The Relationship
Between Social Media Use and Beliefs in Conspiracy Theories and Misinformation. Political Behavior.
2021. https://doi.org/10.1007/s11109-021-09734-6 PMID: 34248238
40. Romano A. Conspiracy theories, explained. Voxcom [Internet]. 2020 8/15/2021. Available from: https://
www.vox.com/21558524/conspiracy-theories-2020-qanon-covid-conspiracies-why.
41. Berinsky A. Rumors and Health Care Reform: Experiments in Political Misinformation. British Journal of
Political Science. 2015; 47(2):241–62. Epub 06/19. https://doi.org/10.1017/S0007123415000186.
42. Clarke S. Conspiracy Theories and the Internet: Controlled Demolition and Arrested Development. Episteme.
2007; 4(02):167–80. https://doi.org/10.3366/epi.2007.4.2.167
43. Simon FM, Camargo CQ. Autopsy of a metaphor: The origins, use and blind spots of the ‘infodemic’.
New Media & Society. 2021. https://doi.org/10.1177/14614448211031908
44. Fletcher R, Robertson CT, Nielsen RK. How Many People Live in Politically Partisan Online News Echo
Chambers in Different Countries? Journal of Quantitative Description: Digital Media. 2021;1. https://doi.
org/10.51685/jqd.2021.020
45. Broniatowski DA, Kerchner D, Farooq F, Huang X, Jamison AM, Dredze M, et al. Twitter and Facebook
posts about COVID-19 are less likely to spread misinformation compared to other health topics. PLOS
ONE. 2022; 17(1):e0261768. https://doi.org/10.1371/journal.pone.0261768 PMID: 35020727
46. Bail C, Guay B, Maloney E, Combs A, Hillygus DS, Merhout F, et al. Assessing the Russian Internet
Research Agency’s impact on the political attitudes and behaviors of American Twitter users in late
2017. Proceedings of the National Academy of Sciences. 2019. https://doi.org/10.1073/pnas.
1906420116 PMID: 31767743
47. Altay S, Hacquin A-S, Mercier H. Why do so few people share fake news? It hurts their reputation. New
Media & Society. 2021;0(0):1461444820969893. https://doi.org/10.1177/1461444820969893
48. Guess A, Nagler J, Tucker J. Less than you think: Prevalence and predictors of fake news dissemination
on Facebook. Science Advances. 2019; 5(1). https://doi.org/10.1126/sciadv.aau4586 PMID: 30662946
49. Allcott H, Gentzkow M, Yu C. Trends in the diffusion of misinformation on social media. Research & Politics.
2019; 6(2):2053168019848554. https://doi.org/10.1177/2053168019848554
50. Sternisko A, Cichocka A, Van Bavel JJ. The dark side of social movements: social identity, non-conformity,
and the lure of conspiracy theories. Current Opinion in Psychology. 2020; 35:1–6. https://doi.org/
10.1016/j.copsyc.2020.02.007 PMID: 32163899
51. Bessi A, Coletto M, Davidescu GA, Scala A, Caldarelli G, Quattrociocchi W. Science vs Conspiracy:
Collective Narratives in the Age of Misinformation. PLoS ONE. 2015; 10(2):e0118093. https://doi.org/
10.1371/journal.pone.0118093 PMID: 25706981
52. Walter AS, Drochon H. Conspiracy Thinking in Europe and America: A Comparative Study. Political
Studies. 2020. https://doi.org/10.1177/0032321720972616
PLOS ONE Conspiracy theories over time
PLOS ONE | https://doi.org/10.1371/journal.pone.0270429 July 20, 2022 19 / 19