Before revision: Economists are often interested in estimating averages with respect to distributions of unobservables . Examples are moments of individual fixed-effects,  average partial effects in discrete choice models , and counterfactual simulations in structural models .
After revision: Economists are often interested in estimating averages with respect to distributions of unobservables , such as moments of individual fixed-effects, average partial effects in discrete choice models , and counterfactual simulations in structural models .