The fundamental problem of external validity is not to generalize from one experiment, so much as to experimentally test generalizable theories. That is, theories that explain the systematic variation of causal effects across contexts. Here we show how the graphical language of causal diagrams...

Vote-buying-or the pre-electoral distribution of private goods in exchange for support at the ballot box-is often blamed for the poor economic performance of many sub-Saharan countries. For instance, vote-buying may undermine accountability and the implementation of sound development policies by...