Abstract This article studies how innovation reacts to climate change and shapes its economic impacts, focusing on U.S. agriculture. We show in a model that directed innovation can either mitigate or exacerbate climate change’s potential economic damage depending on the substitutability between new technology and favorable climatic conditions. To empirically investigate the technological response to climate change, we measure crop-specific exposure to damaging extreme temperatures and crop-specific innovation embodied in new variety releases and patents. We find that innovation has redirected since the mid-twentieth century toward crops with increasing exposure to extreme temperatures. Moreover, this effect is driven by types of agricultural technology most related to environmental adaptation. We next show that U.S. counties’ exposure to induced innovation significantly dampens the local economic damage from extreme temperatures. Combining these estimates with the model, we find that directed innovation has offset 20% of potential losses in U.S. agricultural land value due to damaging climate trends since 1960 and that innovation could offset 13% of projected damage by 2100. These findings highlight the vital importance, but incomplete effectiveness, of endogenous technological change as a source of adaptation to climate change.

We study how social organization shapes patterns of economic interaction and the effects of national policy, focusing on the distinction between age-based and kin-based groups in sub-Saharan Africa. Motivated by ethnographic accounts suggesting that this distinction affects redistribution, we analyze a cash transfer program in Kenya and find that in age-based societies there are consumption spillovers within the age cohort, but not the extended family, while in kin-based societies we find the opposite. Next, we document that social structure shapes the impact of policy by showing that Uganda’s pension program had positive effects on child nutrition only in kin-based societies. (JEL H23, I12, I38, J13, O15, Z13)

This paper studies how governments intervene in agricultural markets to reshape the economic consequences of climate extremes. We construct a global dataset of agricultural policies and extreme heat exposure by country and crop since 1980. Extreme heat shocks to domestic production lead to policies that assist consumers by lowering domestic food prices. This effect is persistent, primarily implemented via border policies, and stronger during election years. Shocks to foreign production induce the opposite response: policies that assist producers by raising prices. These findings can be rationalized by a model in which governments use agricultural policy to redistribute among domestic interest groups. Our estimates imply that policy responses shield domestic consumers, while exacerbating losses for domestic producers and foreign consumers. Policy responses have regressive consequences globally, disproportionately harming poor and heat‐exposed countries.

Robert Gordon's The Rise and Fall of American Economic Growth compellingly shows how technical innovation, stimulated by the country's institutions, has radically improved the living standards of the citizens of the US. We conduct an empirical investigation of the impact of the capacity of the US state, as proxied by the presence of post offices, on innovation. We show that there is a strong association between the number of post offices in a county and patenting activity. Our evidence suggests that part of story of US innovation is the capacity and reach of the US state.

We test the longstanding hypothesis that ethnic groups organized around “segmentary lineages” are more prone to conflict. Ethnographic accounts suggest that in such societies, which are characterized by strong allegiances to distant relatives, individuals are obligated to come to the aid of fellow lineage members when they become involved in conflicts. As a consequence, small disagreements often escalate into larger‐scale conflicts involving many individuals. We test for a link between segmentary lineage organization and conflict across ethnic groups in sub‐Saharan Africa. Using a number of estimation strategies, including a regression discontinuity design at ethnic boundaries, we find that segmentary lineage societies experience more conflicts, and particularly ones that are retaliatory, long in duration, and large in scale.

We present evidence that the traditional structure of society is an important determinant of the scope of trust today. Within Africa, individuals belonging to ethnic groups that organized society using segmentary lineages exhibit a more limited scope of trust, measured by the gap between trust in relatives and trust in non-relatives. This trust gap arises because of lower levels of trust in non-relatives and not higher levels of trust in relatives. A causal interpretation of these correlations is supported by the fact that the effects are primarily found in rural areas where these forms of organization are still prevalent.