Replication can often be thought of as a useful tool to train graduate students or as a starting point for a new line of research, but sometimes replication is necessary as a means to check the robustness of results that can directly influence policy. Recently, Nunn and Qian (US Food Aid and Civil Conflict, American Economic Review 2014; 104: 1630–1666) found that United States (US) food aid increases the incidence and duration of civil conflict in recipient countries. This paper has received significant attention and has even been noticed by the United States Agency for International Development (USAID).
If the results of their study are robust, policymakers can attempt to minimize the predicted negative impacts. In our paper, we first were able to successfully replicate the results of Nunn and Qian (2014) using their data, but alternative software (R instead of Stata). We then attempted to further scrutinize one of their conclusions. Specifically, the authors claim that the adverse effect of US food aid on conflict does not vary across pre-determined characteristics of aid recipient countries (a seemingly strong assumption across sometimes vastly different nations). Nunn and Qian (2014) made attempts to allow for heterogeneity in their regression models by interacting US food aid with these pre-determined characteristics, but this simply amounted to group averages which may miss the underlying heterogeneity.
In order to check for more sophisticated forms of heterogeneity, we used a semiparametric estimation procedure. While the results visually suggested the presence of some amount of heterogeneity, this could not be determined statistically as we were unable to formally reject any of the parametric specifications in Nunn and Qian (2014). The conclusion of such a replication is that their models cannot be rejected using their data and we argue that the results of their paper are robust.
While we rightly criticize studies that cannot be replicated, we should also make note of those that can be replicated. It is typically a non-trivial task and while we were successful, we suggest that this study be further tested with samples from a different set of countries (both recipients and donors) and/or time periods.
Chi-Yang Chu is an assistant professor of economics at National Taipei University. Daniel J. Henderson is a professor of economics and the J. Weldon and Delores Cole Faculty Fellow at the University of Alabama. Le Wang is an associate professor of economics and the Chong K. Liew Chair in Economics at the University of Oklahoma. Correspondence about this blog should be directed to Daniel Henderson at firstname.lastname@example.org.
 N. Nunn and N. Qian, US Food Aid and Civil Conflict. American Economic Review. 104, 1630–1666 (2014)
 C.-Y. Chu, D. J. Henderson and L. Wang. The Robust Relationship between US Food Aid and Civil Conflict. Journal of Applied Econometrics. 32, 1027-1032 (2017)