Farther on down the road: transport costs, trade and urban growth (forthcoming, Review of Economic Studies)
Has climate change driven urbanization in Africa? (with Vernon Henderson and Uwe Deichmann; formerly "50 years of urbanization in Africa: Examining the role of climate"; revision requested, Journal of Development Economics)
Abstract: This paper documents strong but differentiated links between climate and urbanization in Sub-Saharan Africa, which has experienced significant moisture reductions. In large panels of districts and cities, we find drier conditions increase both urbanization and total city incomes in places most likely to have an urban industrial base. In this context, migration to cities provides an “escape” from negative agricultural moisture shocks. However, in most places (75% of our sample), local cities just service agriculture and there is no escape into alternative export-based employment. There, drying has little impact on urban population share or total urban income.
The Global Spatial Distribution of Economic Activity: Nature, History, and the Role of Trade (with Vernon Henderson, Tim Squires and David N. Weil)
Abstract: We study the distribution of economic activity, as proxied by lights at night, across 250,000 grid cells of average area 560 square kilometers. We first document that nearly half of the variation can be explained by a parsimonious set of physical geography attributes. A full set of country indicators only explains a further 10%. When we divide geographic characteristics into two groups, those primarily important for agriculture and those primarily important for trade, we find that the agriculture variables have relatively more explanatory power in countries that developed early and the trade variables have relatively more in countries that developed late, despite the fact that the latter group of countries are far more dependent on agriculture today. We explain this apparent puzzle in a model in which two technological shocks occur, one increasing agricultural productivity and the other decreasing transportation costs, and in which agglomeration economies lead to persistence in urban locations. In countries that developed early, structural transformation due to rising agricultural productivity began at a time when transport costs were still relatively high, so urban agglomerations were localized in agricultural regions. When transport costs fell, these local agglomerations persisted. In late-developing countries, transport costs fell well before structural transformation. To exploit urban scale economies, manufacturing agglomerated in relatively few, often coastal, locations. With structural transformation, these initial coastal locations grew, without formation of more cities in the agricultural interior.
Is urbanization in sub-Saharan Africa different?(with Vernon Henderson and Mark Roberts)
Abstract: In the past dozen years, a literature has developed arguing that urbanization has unfolded differently in post-independence sub-Saharan Africa than in the rest of the developing world, with implications for African economic growth overall. While African countries are more urbanized than other countries at comparable levels of income, it is well-recognized that total and sector GDP data are of very low quality, especially in Africa. When viewed from the perspective of effective technology as suggested in endogenous growth frameworks (and as proxied by educational attainment), the African urbanization experience overall matches global patterns. There are differences, however, at a sector level. Agricultural trade price shocks have a differential effect in Africa, but not what is postulated in some of the literature. In our data, shocks that improve farm prices deter African urbanization, as might be expected in simple two sector models. In the remainder of the developing world, such shocks promote urbanization. The paper explores potential reasons for this difference, looking, in particular, at differences in land ownership institutions and the likelihood of agricultural surpluses being invested in urban production. Shocks to modern manufacturing spur urbanization in the rest of the developing world, but effects are dependent on the level of development and implied ability to accommodate the shocks. Thus many countries in Africa, with their lower level of development, do not respond to these shocks. Finally, historical indicators of the potential for good institutions promote urbanization both inside and outside of Africa.
Dowry Deaths: response to weather variability in India (2014; with Sheetal Sekhri) Journal of Development Economics 111: 212-223. (ungated version)
Abstract: We examine the effect of rainfall shocks on dowry deaths using data from 583 Indian districts for 2002-2007. We find that a one standard deviation decline in annual rainfall from the local mean increases reported dowry deaths by 7.8 percent. Wet shocks have no apparent effect. We examine patterns of other crimes to investigate if increase in general unrest during economic downturn explains the results but do not find supportive evidence. Women's political representation in the national parliament has no apparent mitigating effect on dowry deaths.
Global trends in emerging infectious diseases (2008; with Kate E. Jones, Nikkita G. Patel, Marc A. Levy, Deborah Balk, John L. Gittleman and Peter Daszak), Nature 451: 990-993.
Abstract: Emerging infectious diseases (EIDs) are a significant burden on global economies and public health. Their emergence is thought to be driven largely by socio-economic, environmental and ecological factors, but no comparative study has explicitly analysed these linkages to understand global temporal and spatial patterns of EIDs. Here we analyse a database of 335 EID 'events' (origins of EIDs) between 1940 and 2004, and demonstrate non-random global patterns. EID events have risen significantly over time after controlling for reporting bias, with their peak incidence (in the 1980s) concomitant with the HIV pandemic. EID events are dominated by zoonoses (60.3% of EIDs): the majority of these (71.8%) originate in wildlife (for example, severe acute respiratory virus, Ebola virus), and are increasing significantly over time. We find that 54.3% of EID events are caused by bacteria or rickettsia, reflecting a large number of drug-resistant microbes in our database. Our results confirm that EID origins are significantly correlated with socio-economic, environmental and ecological factors, and provide a basis for identifying regions where new EIDs are most likely to originate (emerging disease 'hotspots'). They also reveal a substantial risk of wildlife zoonotic and vector-borne EIDs originating at lower latitudes where reporting effort is low. We conclude that global resources to counter disease emergence are poorly allocated, with the majority of the scientific and surveillance effort focused on countries from where the next important EID is least likely to originate.