Inside the War on Drugs: Effectiveness and Unintended Consequences of a Large Illicit Crops Eradication Program in Colombia

This article reports the results of an econometric evaluation of the effects of Plan Colombia, the largest US aid package ever received by a country in the western hemisphere. We assess how the aerial spraying of illegal crops affects both the size of the land cultivated with coca bushes as well as the dynamics of localized violence in the context of Colombia’s armed conflict. In particular, we show that the marginal effect of spraying of one acre of coca reduces the cultivated area by about 11 percent of an acre. Since aerial spraying may shift coca crops to neighboring municipalities, this results should be interpreted as a local effect. In addition, since the same coca fields are often sprayed multiple times, this figure constitutes a lower bound of the mean eradicating effect of aerial spraying, To study the impact on conflict dynamics, we examine both the shortterm and the long-term effects of crop spraying. Our results suggest that guerrilla-led violence increases both in the short and the long term. We interpret this result as evidence that the guerrilla tries to hold on violently to the control of an asset that is of first order importance for their survival.