Instrumental Variables in the Long Run

In the field of long-run economic growth, it is common to use historical or geographical variables as instruments for contemporary endogenous regressors. We study the interpretation of these conventional instrumental variable (IV) regressions in a simple, but general, framework. We are interested in estimating the long-run causal effect of changes in historical conditions. For this purpose, we develop an augmented IV estimator that accounts for the degree of persistence in the endogenous regressor. We apply our results to estimate the long-run effect of institutions on economic performance. Using panel data, we find that institutional characteristics are imperfectly persistent, implying that conventional IV regressions overestimate the long-run causal effect of institutions. When applying our augmented estimator, we find that increasing constraints on executive power from the lowest to the highest level on the standard index increases national income per capita three centuries later by 1.2 standard deviations.