ABSTRACT
Confounding poses pervasive problems in the social sciences. For example, does granting property titles to poor land squatters boost access to credit markets, thereby fostering broad socioeconomic development (De Soto 2000)? To investigate this question, researchers might compare poor squatters who possess land titles to those who do not. However, di erences in access to credit markets could in part be due to factors-such as family background-that also make certain poor squatters more likely to acquire titles to their property. Investigators may seek to control for such confounders, by comparing titled and untitled squatters with similar family backgrounds. Yet, even within strata de ned by family background, there may be other di cult-to-measure confounders-such as determination-that are associated with obtaining titles and that also in uence economic and political behaviors. Conventional quantitative methods for dealing with confounding, such as multivariate regression, require other essentially unveri able modeling assumptions to be met, which is a further di culty.
