It has been proposed that malaria, history’s deadliest disease, may be responsible for the death of half the people who have ever lived. In BSE Working Paper 1220, “Social Adaptation to Diseases and Inequality: Historical Evidence from Malaria in Italy,” authors Paolo Buonanno, Elena Esposito and Giorgio Gulino study the ramifications of the way society adapted to the threat posed by this disease. Responses affected where people settled and also how and what they farmed. These factors have had considerable and long-lasting effects on local inequalities.

The “Italian national disease”

Italy is taken as a case study since it has a particularly painful and significant history with malaria. It was indeed termed the “Italian national disease,” and no other European country suffered a comparable death toll.

Alongside the constant risk of malaria, perhaps the second-greatest affliction in Italy was land inequality. Despite the changing sociodemographic structure which was occurring at the time, redistribution efforts did not materialize in malaria-infested areas. This is most clearly seen by comparing the prevalence of malaria to the level of land inequality up and down the country (Figure 1):

The spatial correlation is stark, and the authors exploits an empirical strategy to identify the causal effect of malaria presence on landowner distribution. 

A constant risk

By far the greatest challenge posed by the disease was the constant uncertainty and risk. The consequences were felt both by farm employees and small landowners. Clearly, working in malaria-infested areas exposed agricultural workers to the threat of illness and death. This was compounded by the fact that the malaria season coincided exactly with the peak of the agricultural season, which meant farmworkers had to expose themselves to the disease in order to survive.

The authors present various channels through which the coping strategies implemented to mitigate the risk of contagion in turn fostered the observed land inequality.

First, malaria-affected municipalities were not, in fact, less-densely inhabited, but were occupied differently. Settlement patterns offered protection from contagion, and could be life-saving for children and pregnant women. However, in order to reduce exposure, families had to locate their houses far from malaria-infested fields. The increased distance limited access to work for many agricultural laborers. Additionally, this pattern increased the cost for small farms of replacing labor, hiring new workers and general farm management as workers fell sick. Quite quickly, the task could become cumbersome. In contrast, large farms were organized precisely in such a way as to meet the demand and take advantage of the harvest.

Second, malaria-infested municipalities were not less cultivated, but were cultivated differently, privileging labor-saving farming activities. Large farms could more easily diversify production, allowing them to hedge against particularly unhealthy years. Labor-saving crops and farming activities, such as cereals and sheep husbandry, could minimize worker-inputs. Naturally, plants that required little effort during the malaria season, and thus reduced the need to expose a valuable workforce, were popular alternatives. However, this diversification of production was often not the most profitable choice for small family farms and could not guarantee subsistence. Gradually, these practices entrenched local land inequalities.

Empirical challenges

The authors collected new data on land ownership distribution at the municipality level and mapped from historical to present-day municipalities to build several measures of land inequality. Efforts to detect a causal relationship are complicated by two main empirical issues:

• Malaria-infested areas might have differed from other areas due to geographic and climatic characteristics that could, in principle, have also driven landownership concentration.
• The effects of malaria might have been even more persistent in remote places with a history of dysfunctional governments, limited drainage projects, and inadequate public investments to counter the disease. 

The authors lean on decades of research in malaria epidemiology to construct an index for the prevalence of malaria. To better proxy for actual historical malaria risk, the authors use historical data on seasonal temperatures, since malaria transmission is strictly related to local weather conditions. They are able to make clever use of bio-climatic characteristics to predict localized malaria transmission rates. Furthermore, they increase precision by constructing a highly disaggregated measure of temperature. In doing so, the authors are able to estimate the causal relationship of malaria affliction rates on the level of inequality.

Social adaptation and rising inequality

The authors consistently observe a positive relationship between malaria risk and land inequality. The share of land occupied by small farms is reduced by the rate of malaria and vice versa, increased for larger farms. Specifically, being in a municipality with malaria reduced the land share held by small farms by 39 percentage points, which corresponds to a 77% reduction with respect to the mean. They find that large firms were better positioned to absorb health shocks and, in areas with a higher prevalence of malaria, there was a significant increase in the number of landless farmers alongside an increase in the hiring of day laborers. 

Overall, they observe an increase in the Gini index of around 22 percentage points, which points to a significant shift in the level of inequality. Through their careful empirical process, these changes can be put down to the increased presence of malaria.

The authors then extend their analysis to the present day. In doing so, they reveal that, indeed, historical malaria prevalence hampered long-term development. To this day, historically affected municipalities remain poorer and continue to have comparatively lower average levels of human capital. 

Recent medical developments and experimental evidence suggest that a malaria vaccine granting full protection against the disease might soon become available. Given the clear and pertinent results of this paper, the potential social gains in terms of reduced mortality and morbidity, higher human capital accumulation, and productivity of affected areas are enormous.