We examine the generalizability of internally valid estimates of causal effects in a fixed population over time when that population is subject to aggregate shocks. This temporal external validity is shown to depend upon the distribution of the aggregate shocks and the interaction between these...

We show empirically using panel data at the plot and farm level and based on a model incorporating supervision costs, risk, credit-market imperfections and scale-economies associated with mechanization that small-scale farming is inefficient in India. Larger farms are more profitable per acre,...