The relationship of age to voting turnout over a 20-year period is analyzed in a multivariate model with controls for causal covariates and “period” and “cohort” effects. The observed curvilinear pattern of turnout with age remains after holding rival factors constant, but the apparent curvilinearity of cohort membership disappears. Instead, a pattern of decreasing turnout among successively younger birth cohorts is found, suggesting differences in the political socialization of voting obligations between the nineteenth and twentieth centuries.