Over the past four decades, the U.S. economy has seen a decline in the share of young firms alongside a rise in the profit share of GDP. This paper explores how population aging contributes to these twin trends through a demand-side channel. The core hypothesis is that younger households exhibit lower consumer inertia—a tendency to stick with previously chosen products—than older households. As demand shifts toward more inertial consumers, entry becomes harder, incumbents raise markups, and market share tilts toward larger firms. To quantify this mechanism, I develop and calibrate a firm dynamics model with overlapping generations of consumers who differ in their degree of inertia. Using detailed micro data, I show that younger households are significantly less inertial. The model implies that population aging accounts for 20%–30% of the observed decline in young firms and rise in profits. Reduced-form evidence across U.S. states and product categories supports the model’s predictions.

This paper studies the effect of nonlinear pricing on markups and misallocation. In a general equilibrium model in which firms are allowed to set a quantity-dependent pricing schedule, markup heterogeneity is not a sign of misallocation. Instead, we point to a new source of misallocation: high-taste consumers are allocated too much of each good, low-taste consumers too little. Using micro data from the retail sector, we show that nonlinear pricing is prevalent and quantify the model. Welfare losses from misallocation across consumers are substantially larger than those from misallocation across firms under linear pricing.

We use new, comprehensive micro data on oil fields to build and estimate a structural model of the oil industry embedded in a general equilibrium model of the world economy. In the model, firms that belong to Organization of the Petroleum Exporting Countries (OPEC) act as a cartel. The remaining firms are a competitive fringe. We use the model to study the macroeconomic impact of the advent of fracking. Fracking weakens the OPEC cartel, leading to a large long-run decline in oil prices. Fracking also reduces the volatility of oil prices in the long run because fracking firms can respond more quickly to changes in oil demand.