Recent studies appear to show that democracy has no robust association with economic growth. Yet all such work assumes that the causal effect of democracy can be measured by a country's regime status in a particular year (T), which is correlated with its growth performance in a subsequent period (T+1). The authors argue that democracy must be understood as a stock, rather than a level, measure. That is, a country's growth performance is affected by the number of years it has been democratic, in addition to the degree of democracy experienced during that period. In this fashion, democracy is reconceptualized as a historical, rather than a contemporary, variable—with the assumption that long-run historical patterns may help scholars to understand present trends. The authors speculate that these secular-historical infiuences operate through four causal pathways, each of which may be understood as a type of capital: physical capital, human capital, social capital, and political capital. This argument is tested in a cross-country analysis and is shown to be robust in a wide variety of specifications and formats.