What effect does bureaucratic responsiveness have on citizen participation? Since the 1940s, attitudinal measures of perceived efficacy have been used to explain participation. The authors develop a “calculus of participation” that incorporates objective efficacy—the extent to which an individual's participation actually has an impact—and test the model against behavioral data from the online application Fix My Street (n = 399,364). A successful first experience using Fix My Street is associated with a 57 percent increase in the probability of an individual submitting a second report, and the experience of bureaucratic responsiveness to the first report submitted has predictive power over all future report submissions. The findings highlight the importance of responsiveness for fostering an active citizenry while demonstrating the value of incidentally collected data to examine participatory behavior at the individual level.