Social vulnerability to drought is complex but is reflected by the social capacity to anticipate, cope with and respond to drought. Here we estimate these aspects of social vulnerability evaluating the natural resource structure, the economic capacity, the human and civic resources, and aspects of agricultural innovation. The weight of each component of the index is a key determinant of the final value. Here we present the results of the index under two valuation scenarios. In the first one, all components are valued equally. In the second one, the human resources component is given 50 percent of the weight, the economic and natural resource components are given 20 percent of the weight each, and the agricultural technology is given 10 percent of the weight. This reflects the assumption that a society with institutional coordination and strengths for public participation is less vulnerable to drought and that agriculture is only one of the sectors affected by drought. The vulnerability index establishes robust conclusions since the range of values across countries does not change with the assumptions under the two scenarios.