Research

Working papers

Using multiple outcomes to adjust standard errors for spatial correlation (pdf)

With Stefano DellaVigna, Guido Imbens, and David Ritzwoller

Abstract: Empirical research in economics often examines the behavior of agents located in a geographic space. In such cases, statistical inference is complicated by the interdependence of economic outcomes across locations. A common approach to account for this dependence is to cluster standard errors based on a predefined geographic partition. A second strategy is to model dependence in terms of the distance between units. Dependence, however, does not necessarily stop at borders and is typically not determined by distance alone. This paper introduces a method that leverages observations of multiple outcomes to adjust standard errors for cross-sectional dependence. Specifically, a researcher, while interested in a particular outcome variable, often observes dozens of other variables for the same units. We show that these outcomes can be used to estimate dependence under the assumption that the cross-sectional correlation structure is shared across outcomes. We develop a procedure, which we call Thresholding Multiple Outcomes (TMO), that uses this estimate to adjust standard errors in a given regression setting. We show that adjustments of this form can lead to sizable reductions in the bias of standard errors in calibrated U.S. county-level regressions. Re-analyzing nine recent papers, we find that the proposed correction can make a substantial difference in practice.

Updated April 2025

Political polarization in medicine (pdf)

Abstract: Political polarization is increasingly affecting policymaking, but how is it influencing professional decision-making? This paper studies the differences in medical practice between Republican and Democratic physicians over 1999-2019. It links physicians in the Medicare claims data with their campaign contributions to determine their party alignment. In 1999, there were no partisan differences in medical expenditure per patient. By 2019, Republican physicians are now spending 13% more, or $70 annually per patient. We analyze four potential sources of this partisan difference: practice characteristics (i.e., specialization and location), patient composition, preferences for financial gain, and beliefs about appropriate care. Even among physicians in the same specialty and location treating patients for the same condition, Republican physicians spend 6% more, especially on elective procedures. Using a movers design, we also find large partisan differences for treating the same patient. We find no evidence that these partisan differences are driven by profit incentives. Instead, the evidence points to diverging beliefs. Republican physicians adhere less to clinical guidelines, consistent with their reported beliefs in prior surveys. The timing of the divergence matches the politicization of evidence-based medicine in Congress. These results suggest that political polarization may lead to partisan differences in the beliefs and behavior of practitioners.Updated November 2024

Policy diffusion and polarization across U.S. states (pdf)

With Stefano DellaVigna

Revise and resubmit, Review of Economic Studies

Abstract: Economists have studied the impact of numerous state laws, from welfare rules to voting ID requirements. Yet for all this policy evaluation, what do we know about policy diffusion—how these policies are introduced and spread from state to state? We present a series of facts based on a data set of 602 U.S. state policies spanning the past 7 decades. First, proxies of state capacity do not predict a higher likelihood of innovating new policies, but the political leaning of the state does predict a higher likelihood of introducing partisan laws since 1990. Second, the diffusion of policies from 1950 to 2000 is best predicted by proximity—a state is more likely to adopt a policy if nearby states have already done so—as well as similarity in voter policy preferences. Third, since 2000, party alignment has become the strongest predictor of diffusion, and the speed of adoption has increased. Models of learning and correlated preferences can account for the earlier patterns, but the findings for the last two decades indicate a sharply increasing role of party control. We conclude that party polarization has emerged as a key factor recently for policy adoption, plausibly leading to a worse match between state policies and voter preferences.Updated November 2024

Publications

“Don’t you plan on voting?” The motives and effects of peer pressure in voter mobilization (pdf, doi)

Quarterly Journal of Political Science (2025)

Abstract: This paper studies the motives behind socially pressuring others in the context of voter mobilization. In this online experiment, college students choose whether to send an email that pressures their campus peers to register to vote for the 2020 U.S. Elections. The senders have a negative average willingness-to-pay (WTP) to send the email, meaning they would rather pay than pressure their peers. The experiment reveals two counteracting motives at play. On the positive side, senders believe that pressuring their peers will persuade them to register. On the negative side, they believe that their peers will dislike being pressured, which outweighs the positive motives. However, under anonymous messaging, they become much less sensitive to whether the recipient dislikes being pressured, and their average WTP turns positive. This pattern of behavior reflects voters who are motivated by the prospect of mobilizing their peers, but are restrained by self-interested concerns from social costs or retaliation.

Bottlenecks for evidence adoption (pdf, doi)

With Stefano DellaVigna and Elizabeth Linos

Journal of Political Economy (2024)

Abstract: Governments increasingly use randomized controlled trials (RCTs) to test innovations, yet we know little about how they incorporate results into policymaking. We study 30 US cities that ran 73 RCTs with a national nudge unit. Cities adopt a nudge treatment into their communications in 27% of the cases. We find that the strength of the evidence and key city features do not strongly predict adoption; instead, the largest predictor is whether the RCT was implemented using preexisting communication, as opposed to new communication. We identify organizational inertia as a leading explanation: changes to preexisting infrastructure are more naturally folded into subsequent processes.

Television and American consumerism (pdf, doi)

Journal of Public Economics (2022)

Abstract: How did the introduction of mass commercial television in the postwar era change American consumer behavior? Media scholars and U.S. historians claim that TV with its unprecedented advertising appeal drew Americans into a culture of upscaling and purchasing products for social status. I test this prevailing theory using newly digitized nationwide county-level retail sales data from the Census of Business series. I compare growth in retail sales between areas with and without local TV service over the unanticipated Federal Communications Commission (FCC) Freeze, which halted the licensing of new TV stations from 1948–52. I find three results that corroborate TV’s long-attributed role in American consumerism. First, during the Freeze, total retail sales in counties with TV access increased by 3–4% more on average than in counties without access. Second, the effect of TV was concentrated in the automobile sector, which alone accounted for a third of the total difference. Third, TV advertising led to higher growth in sales, but only for durable goods, which neatly aligns with both qualitative reports and theories of conspicuous consumption. Historians also propose that the suburban family life popularized in TV sitcoms became the mainstream representation of the American Dream in the 1950s. Consistent with these accounts, I find that the start of TV access coincides with greater activity in local highway construction and birthrates.

Work in progress

Policy diffusion across countries

With Stefano DellaVigna and David Yang

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