While sharing intellectual ancestry, organizational ecology and institutionalism are rarely used conjointly to explain population dynamics. A rapprochement would nevertheless be fruitful, as the parsimonious models developed by ecologists are better able to explain organizational founding and failure when enriched with institutional variables. We present a meta-analysis of density dependence theory, which predicts a non-monotonic relationship between population density and organizational vital events. We show that ecology and institutionalism are ‘better together’ by extending this ecological framework in four institutionalism-inspired ways. First, we show that the effects of density on organizational vital rates are moderated by two conceptions of time: ecological ‘clocks’ and institutional ‘eras’. Second, we argue that the socio-political legitimacy of organizational forms, a concept with strong institutional roots, exacerbates density-related founding while attenuating failure. Third, we illustrate how the emergence of prototypical categories in organizational fields can increase the magnitude of density effects. Fourth, we highlight how these socio-political legitimacy and categorization effects are conditioned by ecological clock time. We close by proposing a concise agenda for future research, aimed at finding a better balance between the generality and explanatory power of our most trusted organizational theories.