Replication Data for: On the Internet, No One Knows You’re an Activist: Patterns of Participation and Response in an Online, Opt-in Survey Panel

Recent years have seen a dramatic increase in surveys of online respondents who participate absent random selection. Using an uncompensated, opt-in panel of 11,000 Pennsylvanians (2020-2022), we benchmark self-reports against vote histories, campaign contributions, election returns, and Census data. Ours is among the first such benchmarking exercises in more than a decade, a period when online survey research has transformed. It is also among the first analyzing a longitudinal panel. Our panelists are approximately balanced on partisanship; attrition is limited. Notably, respondents are very politically engaged, with high rates of turnout, campaign contributions, and rally attendance. Ethnic/racial minorities are under-represented. Political attitudes show high over- time stability, and an experiment uncovers few partisan differences in response rates. Such survey samples are cost-effective ways to track the views of highly engaged citizens over time, but lower- engagement citizens prove hard to recruit, even with supplemental efforts. Survey participation is itself a political behavior.