Authors such as Collier and Hoeffler (2004) argue that declines in the opportunity cost of rebelling increase the probability of civil war. This paper examines this theory using a tragic natural experiment: the HIV/AIDS epidemic in sub-Saharan Africa. Since 1990, the epidemic has claimed more than 20 million lives in the region and lowered life expectancies by as much as 25 years. These dramatic declines in life expectancies substantially reduced the opportunity cost of dying in combat and, therefore, should have increased the likelihood of civil war. Using male circumcision rates as an instrument for HIV prevalence and, subsequently, for life expectancy, this paper finds that a one-year increase in life expectancy decreases the probability of civil war by 0.7 percentage points. The result is significant at the 5 per cent level. This supports the theory that pecuniary and non-pecuniary opportunity costs are important determinants of conflict onset.
