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.
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.