1. Mostly Harmless Econometrics
2. Identification of causal effects using instrumental variables;Angrist;Journal of the American Statistical Association,1996
3. BC also provide reduced-form regressions, linking rainfall to democratic transitions, which are not discussed in the following. In a separate paper, I provide a more extended discussion as well as a replication of Miguel, Satyanath, and Sergenti (2004), who use rainfall as an instrument to evaluate the effect of economic shocks on the onset of civil conflict. Their main findings from 2SLS are corroborated by the rank-based HL estimates. See, however, Ciccone (2011), who points out several problems with the specification of Miguel, Satyanath, and Sergenti (2004).
4. An alternative explanation for the differences between the 2SLS and the HL point estimates would be the presence of unusually high outcomes on the dependent variable. If the “unusual” outcomes are considered aberrant, then the rank-based estimate is still preferable. However, Keele, McConnaughy, and White (2012, 489) point out that, if one has reason to believe that the “unusual” outcomes are accurately reflecting the relationship in the data (and hence are due to “unusual” values of the treatment), then a mean-based estimate might be preferable to a rank-based estimate, since the “unusual” observations may contain particularly valuable information. In the sample of BC, the difference between the rank-based HL estimates and the mean-based 2SLS cannot be explained by dropping the most extreme observations.
5. Comparing Partial Likelihood and Robust Estimation Methods for the Cox Regression Model