This project examines the impact of parasitic diseases on the productivity of populations of different ancestral heritages in the early 20th-century American South. The research has historical significance because it quantifies the relationship between endemic parasitic diseases and the economic well-being of two historically important populations, African-Americans (blacks) and European-Americans (whites). The project helps explain the economic development of the American South and address questions concerning the productivity of 19th-century southern slavery. The research focuses on the geographical distinctiveness of diseases and the differential biological susceptibilities of blacks and whites to particular endemic diseases, primarily to parasitic hookworm and malaria. The research gathers archival data from the Rockefeller Archive Center on the prevalence of parasitic diseases in the early 20th-century for all available counties for eleven southern states. The project uses the available disease prevalence rates with various climatic, geographical, etiological factors, and other disease-related data to estimate (impute) disease prevalence rates for those southern counties that lack explicit disease data. The research employs the explicit and imputed disease prevalence rates along with agricultural input and output data for 968 southern counties to estimate differences in county-level economic productivity (agricultural output) between black and white agricultural labor. The econometric estimations of productivity control for other pertinent variables and correct for various statistical concerns.
The broader significance of the project is that it provides data for estimating the impact of parasitic diseases in the world today. The role of endemic hookworm and malaria in explaining early 20th-century economic productivity of southern black and white agricultural labor assists in understanding the economic impact of these diseases today. Hookworm currently infects between 20 and 33 percent of the world's population; malaria infects 300 to 500 million people and kills 2 to 3 million per year. The economic impact of these diseases is not known with much precision, but early 20th-century estimates suggest hookworm reduced labor productivity from 20 to 70 percent. Malaria's economic impact is just now being studied. A hypothetical but plausible estimate for the impact of hookworm alone illustrates the possible magnitude of the costs of these diseases. Using the 20 percent hookworm infection rate means that about 1.2 billion people worldwide are infected. If hookworm infects people with a per capita income equivalent of $800 U. S. dollars (people in the world's poorest nations) and reduces annual productivity just 15 percent, the economic losses due to hookworm alone are $144 billion per year. Capitalized at an interest rate of 4 percent, this represents a permanent wealth reduction of $3.6 trillion for the world's poorest peoples. This calculation is imprecise. But it suggests that throughout much of the developing world the control of endemic parasitic diseases may be an effective way to combat poverty. This project's estimation of the lost economic productivity attributable to hookworm and malaria establishes more precise boundaries for estimating the contemporaneous effects of these diseases.
This research project resulted in the publication of a book, Parasites, Pathogens, and Progress: Diseases and Economic Development (MIT Press 2011) that tells a big picture story of the historical evolution of humanity which is an amalgam of the co-evolution of microbiology, the effects and efforts of humans, and economic production. Emphasizing the impact of pathogens on human society, the book integrates economic and microbiological views into an explanation of the historical development of humanity and the economy with specific application to the American experience, its history and economic development. Besides providing a more complete history of American economic development, the big picture offered has implications for the issues of environmental degradation and sustainability. The book documents that environmental changes that affect the issue of sustainability were part and parcel of human experience for at least the past 50,000 years. Throughout history, in the past, present, and future, sustainability depended, depends, and will depend on the population, skills, and capital accessible at that time. While the book has aspects in common with the literature of medical and social historians, it differs in several respects. First, it takes a fundamentally economic approach. Second, it emphasizes the critical interactions among human choices, microorganisms, evolution, and diseases. Third, it views the environment and diseases as evolving phenomena. Fourth, it stresses that disease environments are endogenous to human actions. Fifth, it documents that the establishment and growth of African slavery in America was the result of economic considerations as well as the result of biological traits (the frequencies of various genetic traits) within different populations. Sixth, it shows that the development of the American economy prior to the modern era (twentieth century) was primarily the result of demographic changes, large-scale plantation slavery, and important developments in transportation that combined to spread infectious diseases. The project resulted in the creation of three major databases: (1) A county-level database was created that contains hookworm prevalence rates, malaria morbidity and mortality rates, sanitary conditions, climate data (annual and seasonal temperatures; annual and seasonal precipitation; and frost free days, among other variables), soil and topography data (soil particulate size, drainage conditions, elevation, and coastal location, among other variables), agricultural output and input (including male and female farm workforce estimates) data for all counties (nearly 1,200) in 12 southern states in the early twentieth-century South. (2) A county/community-level database was created that contains hookworm prevalence rates for black and white civilians and for blacks and whites in the US Army for several dozen southern counties/communities in various southern states in the early twentieth-century South. (3) A state-level database was created that contains mortality rates for the state populations and for eight age, gender, and race cohorts for all states in the United States for 1850-1900 for all causes of death and for about two dozen specific causes of death. The project's major findings are: (1) Before the era of modern medicine, sanitation, public health, and low-cost potable water, pathogens that attack and parasitize humans were rampant. The nineteenth century was a watershed; diseases spread and proliferated enormously with advances in transportation and increased urbanization. (2) Large-scale plantation slavery served as a reservoir for diseases and played a major role in their maintenance and spread during the slave era in the United States. (3) Infectious diseases had a major impact on the development of the American economy prior to the modern era. (4) Hookworm and malaria were prevalent throughout the southern United States in the early twentieth-century South. (5) Imputed values for missing observations on hookworm prevalence rates and on malaria morbidity and mortality rates for the early twentieth-century South are consistent with known etiological factors for each disease. Hookworm was more prevalent in warmer and wetter areas with relatively poor sanitary conditions and relatively sandy soils. Malaria morbidity and mortality rates were greater in warmer and wetter areas with relatively poor drainage conditions (and more frequent ponding of water) and more humid coastal areas. (6) In the early twentieth-century South, civilian and US Army whites had significantly greater hookworm infections than civilian and US Army blacks, respectively. The hookworm infection rates of whites were in the range of two (or more) times those of blacks. (7) In the second half of the nineteenth century in the United States: (a) mortality rates were greatest among infants and young children; (b) mortality rates differed substantially across regions; (c) mortality rates for specific causes of deaths differed substantially across causes and regions; (d) mortality rates for upper respiratory diseases were greatest in the Northeast and least in the South; (e) mortality rates for (warm-weather) fevers and intestinal nematodes were greatest in the South and least in the Northeast. (8) Hookworm and malaria infections were likely to have reduced the labor productivity of agricultural workers in the early twentieth-century South.
