The relationship between ethnic heterogeneity and economic growth is complex. Empirical research working with cross-country data finds a negative, or statistically insignificant, relationship. However, analysis at the city level finds a positive effect of diversity on wages and productivity. Generally there is a trade-off between the economic benefits of diversity and the costs of heterogeneity. Using cells of fixed size, we find that the relationship between diversity and growth is positive for small geographical areas. In the case of Africa, we argue that the explanation is the increase in trade at the boundaries between ethnic groups due to ethnic specialization.

Can terrorist attacks be timed to change the outcome of democratic elections? In this paper, we analyze the electoral impact of the terrorist attacks of March 11, 2004, in Madrid. Studies using individual level postelectoral survey data reach contradictory conclusions. We propose an alternative approach. Since the bombings took place only three days before the 2004 congressional election, we can find a control group of individuals who cast their vote before the terrorist attacks. The results indicate that the attacks had an important electoral impact, rejecting the hypothesis that the identity of the winner was unaffected by the terrorist attacks.

The World Health Organization estimates that 300 million clinical cases of malaria occur annually and observed that during the 80s and part of the 90s its incidence increased. In this paper, we explore the influence of refugees from civil wars on the incidence of malaria in the refugee-receiving countries. Using civil wars as an instrumental variable, we show that for each 1,000 refugees there are between 2,000 and 2,700 cases of malaria in the refugee-receiving country. On average 13% of the cases of malaria reported by the WHO are caused by forced migration as a consequence of civil wars.