Matthew Gentzkow’s research while affiliated with Stanford University and other places

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Publications (105)


Effect of stay-at-home orders. Note: Figure plots estimated treatment effects ωk\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\omega _{k}$$\end{document} of stay-at-home orders on different outcomes, using the event-study specification at the CSA-day level outlined in Eq. (1) for the mobility and economic outcomes and Eq. (14) for the health outcomes. Panel A shows the effect on mobility, using the log of total POI visits in the SafeGraph data. Panel B shows the effect on consumer spending, using the log of total spending in Facteus’ debit card sample. Panel C shows the effect on employment, using the log number of individuals with positive work hours from the Homebase sample. Panel D examines log new cases as the outcome and sets γ=0\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\gamma =0$$\end{document} which implies log(Iit)=log(Cit)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\log (I_{it})=\log (C_{it})$$\end{document}. Panel E is the same as Panel D, except that it sets γ=1/6\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\gamma =1/6$$\end{document}. All regressions include date fixed effects δt\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\delta _{t}$$\end{document}. Panels A-C include CSA fixed effects μi\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mu _{i}$$\end{document}; Panels D–E include the event window indicator ξit\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\xi _{it}$$\end{document}. CSAs are weighted by population in the regression. Standard errors are clustered at the CSA level irrespective of order timing
Temporal variation explained by policy. Note: Figure plots the share of the total change in each outcome that is attributable to a given policy PolicyΔ/TotalΔ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\text {Policy}\Delta /\text {Total}\Delta $$\end{document} following Sect. 5.1. Panel A reports estimates using stay-at-home orders and business closure orders for POI visits from SafeGraph, total wages from Homebase, and employment from Homebase. For each policy treatment, we restrict attention to the CSAs treated by the given policy. Panel B reports estimates of the policy-induced change in the contact rate βt\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\beta _{t}$$\end{document} from stay-at-home orders, varying the assumed basic reproduction number R0\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\mathscr {R}}_{0}$$\end{document}. In both panels, the bars depict 95% confidence intervals. See Table 5 for additional details on Panels A and B. Panel C plots observed and counterfactual cases following the methodology outlined in Sect. 5.3 for our sample of cumulative statistical areas (CSAs) using γ=1/6\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\gamma =1/6$$\end{document}. Panel C reports the observed number of cases along with the estimated number of cases if a uniform stay-at-home order was implemented on March 17 with proportional effect on social distancing behaviors, a uniform stay-at-home order was implemented on March 17 that caused social distancing behaviors to fall to a fixed level of 35% of March 1 levels, and the estimated number of cases if all areas followed the same social distancing behavior as the San Francisco Bay Area (defined to be the counties in the San Francisco CSA that were first to implement a stay-at-home order)
Determinants of geographic variation in log contact rates. Note: Figure plots the coefficients of regressing the CSA log contact rate fixed effect estimates θ^i\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\hat{\theta }_{i}$$\end{document} from Eq. (13) on CSA-level determinants. The θ^i\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\hat{\theta }_{i}$$\end{document} and all covariates have been standardized to have a mean 0 and a standard deviation of 1. Panel A plots the standardized coefficients and 95% confidence intervals from univariate regressions. Panel B repeats Panel A but the regressions also control for the log of population. Population weights are not used. Robust standard errors are used to compute the confidence intervals
Distribution of timing of first government order. Note: Figure shows the distribution of government order effective start dates over time and across counties. Each bar represents the number of counties (y-axis) for which the first order of a given type went into effect on the date specified (x-axis). Stay-at-home and business closing orders are shown in blue and orange bars respectively. See Sect. 2.1 for detail on data sources and processing. (color figure online)
Trends in average mobility and health. Note: Figure reports trends in average mobility and health by county order timing and week. Panel A plots the log of daily average POI visits, normalizing relative to the week starting January 29, 2020. Panel B plots the log of daily new COVID-19 cases, normalized to the week starting March 25, 2020. In both panels, averages are weighted by population and taken across counties and days prior to taking logs or normalization. ‘Early Order’ indicates counties with a stay-at-home order on or before March 25, 2020. ‘Late Order’ indicates counties with a stay-at-home order after this point. ‘No Order‘ indicates counties which did not issue a stay-at-home order during this sample period. The dashed vertical line indicates the week starting March 25, 2020

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What explains temporal and geographic variation in the early US COVID-19 pandemic?
  • Article
  • Publisher preview available

December 2024

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1 Read

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5 Citations

Review of Economic Design

Hunt Allcott

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Levi Boxell

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Benny Goldman

We provide new evidence on the drivers of the early US COVID-19 pandemic and develop a methodology that future researchers can use to similarly analyze the outbreaks of new diseases. We combine an epidemiological model of disease transmission with quasi-random variation arising from the timing of stay-at-home-orders to estimate the causal roles of policy interventions and voluntary social distancing. We then relate the residual variation in disease transmission rates to observable features of cities. We estimate significant impacts of policy and social distancing responses, but we show that the magnitude of policy effects was modest, and most social distancing was driven by voluntary responses. Moreover, we show that neither policy nor rates of voluntary social distancing explained a meaningful share of geographic variation. The most important predictors of which cities were hardest hit by the pandemic were exogenous characteristics such as population and density.

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Fig. 1. Share of participants using Facebook and Instagram during study period. Note: This figure presents the share of Deactivation and Control groups that used Facebook and Instagram on each day. "Use" is defined as logging in and seeing five or more pieces of content. The dark gray shaded area indicates the Control group's 7-d deactivation period, while the light gray shaded area indicates the Deactivation group's 35-d additional deactivation period. We exclude Facebook use data from October 27th due to a logging error.
The effects of Facebook and Instagram on the 2020 election: A deactivation experiment

May 2024

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187 Reads

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10 Citations

Proceedings of the National Academy of Sciences

We study the effect of Facebook and Instagram access on political beliefs, attitudes, and behavior by randomizing a subset of 19,857 Facebook users and 15,585 Instagram users to deactivate their accounts for 6 wk before the 2020 U.S. election. We report four key findings. First, both Facebook and Instagram deactivation reduced an index of political participation (driven mainly by reduced participation online). Second, Facebook deactivation had no significant effect on an index of knowledge, but secondary analyses suggest that it reduced knowledge of general news while possibly also decreasing belief in misinformation circulating online. Third, Facebook deactivation may have reduced self-reported net votes for Trump, though this effect does not meet our preregistered significance threshold. Finally, the effects of both Facebook and Instagram deactivation on affective and issue polarization, perceived legitimacy of the election, candidate favorability, and voter turnout were all precisely estimated and close to zero.


Pricing Power in Advertising Markets: Theory and Evidence

February 2024

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26 Reads

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9 Citations

American Economic Review

Existing theories of media competition imply that advertisers will pay a lower price in equilibrium to reach consumers who multi-home across competing outlets. We generalize and extend this theoretical result and test it using data from television and social media advertising. We find that the model is a good match, qualitatively and quantitatively, to variation in advertising prices across demographic groups, outlets, platforms, and over time. We use the model to quantify the effects of competition within and across platforms. (JEL G34, K21, L13, L82, M37)






Reshares on social media amplify political news but do not detectably affect beliefs or opinions

July 2023

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171 Reads

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69 Citations

Science

We studied the effects of exposure to reshared content on Facebook during the 2020 US election by assigning a random set of consenting, US-based users to feeds that did not contain any reshares over a 3-month period. We find that removing reshared content substantially decreases the amount of political news, including content from untrustworthy sources, to which users are exposed; decreases overall clicks and reactions; and reduces partisan news clicks. Further, we observe that removing reshared content produces clear decreases in news knowledge within the sample, although there is some uncertainty about how this would generalize to all users. Contrary to expectations, the treatment does not significantly affect political polarization or any measure of individual-level political attitudes.


Like-minded sources on Facebook are prevalent but not polarizing

July 2023

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307 Reads

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117 Citations

Nature

Many critics raise concerns about the prevalence of ‘echo chambers’ on social media and their potential role in increasing political polarization. However, the lack of available data and the challenges of conducting large-scale field experiments have made it difficult to assess the scope of the problem1,2. Here we present data from 2020 for the entire population of active adult Facebook users in the USA showing that content from ‘like-minded’ sources constitutes the majority of what people see on the platform, although political information and news represent only a small fraction of these exposures. To evaluate a potential response to concerns about the effects of echo chambers, we conducted a multi-wave field experiment on Facebook among 23,377 users for whom we reduced exposure to content from like-minded sources during the 2020 US presidential election by about one-third. We found that the intervention increased their exposure to content from cross-cutting sources and decreased exposure to uncivil language, but had no measurable effects on eight preregistered attitudinal measures such as affective polarization, ideological extremity, candidate evaluations and belief in false claims. These precisely estimated results suggest that although exposure to content from like-minded sources on social media is common, reducing its prevalence during the 2020 US presidential election did not correspondingly reduce polarization in beliefs or attitudes.


Citations (76)


... Many studies seek to empirically distinguish the effects of government interventions from those of voluntary social distancing, see e.g. (Allcott et al., 2020;Goolsbee & Syverson, 2021;Sheridan et al., 2020). Findings vary widely, and in a review of the literature, (Meunier & Bricongne, 2021) find that the effects attributed to lockdown measures range from 12% to 60%. ...

Reference:

Optimal intervention strategies for a new pandemic: The case of Covid-19
What explains temporal and geographic variation in the early US COVID-19 pandemic?

Review of Economic Design

... As these platforms have become integrated into our daily lives, transforming into essential tools for information diffusion 3,4 and personal communication 5 , they have merged entertainment-driven business models with complex social dynamics 6 , raising significant concerns about their potential impact on social dynamics 7-11 . Offering unprecedented opportunities for content to achieve rapid and widespread attention 12,13 , social media have become crucial environments for the spread of information and misinformation worldwide 14,15 , especially during sensitive periods such as global elections 16,17 . ...

The effects of Facebook and Instagram on the 2020 election: A deactivation experiment

Proceedings of the National Academy of Sciences

... Finally, ecologically valid experimental methods, such as those working directly with tech companies, can help identify the effects of turning 'on' and 'off' different features. For example, Meta recently partnered with researchers to conduct a largescale intervention testing how algorithmically curated vs. chronological feeds on Instagram and Facebook changed voting behavior (Guess et al., 2023). Research identifying temporal and causal effects, particularly long-term effects across childhood and adolescence, is critical for the development of effective prevention and intervention strategies. ...

How do social media feed algorithms affect attitudes and behavior in an election campaign?
  • Citing Article
  • July 2023

Science

... Compared to previous studies that may focus on targets such as feelings towards parties or figureheads (Aslett et al. 2022;Casas, Menchen-Trevino, and Wojcieszak 2023;Guess et al. 2023), we refrained from attempts to change very general attitudes that might be more stable (Peffley and Hurwitz 1985) and queried attitudes towards policies, and, secondly, even more low-level targets as policy-specific issues. We find targeting attitudes towards policies to be a promising avenue. ...

Reshares on social media amplify political news but do not detectably affect beliefs or opinions
  • Citing Article
  • July 2023

Science

... The API only provides information about a tweet and its sender but not its recipients. While the potential mismatch of audience and recipient values poses a limitation, previous research indicates that people tend to expose themselves to social media content that aligns with their worldview (Bakshy et al., 2015;González-Bailón et al., 2023) and moral values (Dehghani et al., 2016;Singh et al., 2021). Thus, it is likely that audience engagement measured in Study 3 were captured from message recipients whose moral values matched those of the message sender. ...

Asymmetric ideological segregation in exposure to political news on Facebook
  • Citing Article
  • July 2023

Science

... In this paper, we simulate a networked system, where thousands of agents, solely driven by LLMs, freely establish social relationships, communicate, and form opinions on political issues. We discover that these free-form social interactions among LLM agents result in the emergence of opinion polarization, a phenomenon widely observed in human society [28,[33][34][35][36][37][38]. Meanwhile, LLM agents spontaneously organize their own social network of human-like properties: agents with homophilic opinions tend to cluster, while those with opposing opinions tend to avoid interactions /citelaiposition. ...

Like-minded sources on Facebook are prevalent but not polarizing

Nature

... Finally, the need for a better understanding of the work-to-politics relationship is amplified by recent developments, where democracies have witnessed the emergence of populist parties worldwide (e.g., Boxell Gentzkow, & Shapiro, 2024;Moss & O'Connor, 2020;Müller, 2017), posing a potential risk to democratic beliefs and stability (e.g., Norris & Inglehart, 2019). With the predicted rise of automation, the accompanying change to job functions, and the restructuring of organizations, there is concern that processes of technological change in the workplace might spill over into a political radicalization or alienation of workers (Gallego & Kurer, 2022). ...

Cross-Country Trends in Affective Polarization
  • Citing Article
  • January 2022

Review of Economics and Statistics

... This involves the frequent organization of meetings, workshops, and debates, which can have a broader impact when covered by the media, which can comment on the themes addressed with varying degrees of critical analysis. scholars argue that as of 2015, digital news was still in its early stages (Gentzkow & Shapiro, 2015). In conclusion, although citizens increasingly devote time to digital media consumption, newspapers continue to hold a critical position within the broader news landscape (Cagé, 2020). ...

Chapter 6 - Ideology and Online News / Matthew Gentzkow and Jesse M. Shapiro
  • Citing Chapter
  • January 2015

... They arise, for instance, in the presence of congestion problems, data leakages, and spillovers, for example when data can reveal information about not only the data subject in question, but also others (Bergemann et al., 2022;Acemoglu, 2022). Negative externalities can also arise due to addiction problems created by viral content (see Allcott et al., 2022). ...

Digital Addiction
  • Citing Article
  • July 2022

American Economic Review