Sparse histogram methods can be useful for returning differentially private counts of items in large or infinite histograms, large group-by queries, and more generally, releasing a set of statistics ...with sufficient item counts. We consider the Gaussian version of the sparse histogram mechanism and study the exact epsilon, delta differential privacy guarantees satisfied by this mechanism. We compare these exact epsilon, delta parameters to the simpler overestimates used in prior work to quantify the impact of their looser privacy bounds.
Previous studies have documented that the increase in the incumbency advantage in the 1960s did not decrease the probability of defeat of incumbents in the U.S. House. I define a method for ...establishing bounds on the probability of incumbent defeat and find that it decreases significantly in the 1950s, before the rise of the incumbency advantage. Incumbency advantage does not have a direct relationship with incumbent defeat rates, raising questions about the use of the incumbency advantage as a means for making inferences about the electoral security of incumbents.
In President Obama's words, the Democratic Party experienced a “shellacking” in the 2010 elections. In particular, the net loss of 63 House seats was the biggest midterm loss suffered by a party ...since 1938—the largest in the lifetimes of approximately 93% of the American population.
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 problem
. 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.
We investigated the effects of Facebook's and Instagram's feed algorithms during the 2020 US election. We assigned a sample of consenting users to reverse-chronologically-ordered feeds instead of the ...default algorithms. Moving users out of algorithmic feeds substantially decreased the time they spent on the platforms and their activity. The chronological feed also affected exposure to content: The amount of political and untrustworthy content they saw increased on both platforms, the amount of content classified as uncivil or containing slur words they saw decreased on Facebook, and the amount of content from moderate friends and sources with ideologically mixed audiences they saw increased on Facebook. Despite these substantial changes in users' on-platform experience, the chronological feed did not significantly alter levels of issue polarization, affective polarization, political knowledge, or other key attitudes during the 3-month study period.
Does Facebook enable ideological segregation in political news consumption? We analyzed exposure to news during the US 2020 election using aggregated data for 208 million US Facebook users. We ...compared the inventory of all political news that users could have seen in their feeds with the information that they saw (after algorithmic curation) and the information with which they engaged. We show that (i) ideological segregation is high and increases as we shift from potential exposure to actual exposure to engagement; (ii) there is an asymmetry between conservative and liberal audiences, with a substantial corner of the news ecosystem consumed exclusively by conservatives; and (iii) most misinformation, as identified by Meta's Third-Party Fact-Checking Program, exists within this homogeneously conservative corner, which has no equivalent on the liberal side. Sources favored by conservative audiences were more prevalent on Facebook's news ecosystem than those favored by liberals.
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.
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.
This dissertation explores how American politics entered the current era where it is characterized by close electoral competition between two increasingly polarized political parties. The first and ...second chapters of the dissertation examine how the changing party identification of the American electorate led to close competition in congressional elections, which had been dominated by the Democratic Party from the 1930s through the 1980s. The first chapter applies a Bayesian changepoint model to identify periods where the macropartisanship of the American public (measured by Gallup surveys from 1950 to 2011) underwent major equilibrium shifts. The model identifies two distinct regimes of American politics, from 1950 to 1983 and 1983 to the present, puncuated by a large decrease in Democratic macropartisanship. The second chapter considers the sources of the equilibrium shift in party identification that was identified in the first chapter and how this equilibrium shift changed the balance of power in elections. Democrats enjoyed a large advantage in party identification until conservative Democrats (both in the South and non-South) shifted out of the party during the 1980s. The Democrats' long standing advantage in party identification had given them a major advantage in House elections and the loss of this advantage made Republicans competitive in congressional elections for the first time since the 1920s. The third chapter examines the electoral incentives for congressional polarization, studying how the ideological extremism of House incumbents has affected their probability of losing during the 20th and early 21st centuries. This chapter shows that incumbents tended to face a higher penalty for extremism during periods of low polarization, so increasing polarization has not hurt the ability of incumbents to win re-election.
