Volume and Direction of the Atlantic Slave Trade, 1650-1870: Estimates by Markov Chain Carlo Analysis

This article presents methods and results in the application of the Markov Chain Monte Carlo (MCMC) analysis to a problem in missing data. The data used here are from The Atlantic Slave Trade Database (TASTD), 2010 version, available online. Of the currently known 35,000 slaving voyages, original data on the size of the cargo of captives exist for some 25 percent of voyage embarkations in Africa and for about 50 percent of arrivals in the Americas. Previous efforts to estimate the missing data (and project the to- tal number of captives who made the transatlantic migration) have proceeded through eclectic projections of maximum likelihood estimates of captives per voyage, without error margins. This paper creates new estimates of total mi- grant flow through two methods: one is a formally frequentist set of multiple methods, and the other is through Markov Chain Monte Carlo methodology. Comparison of the three methods, all based on the same raw data, show that the results of the two new methods are fairly close to one another and they yield total flows of migrant captives of more than 20 percent higher than the previous estimates. Quantitative results, presented in simplified graphs and tables within the text and in detailed spreadsheets available online, provide a new estimate of the volume of African embarkations and American arrivals in the transatlantic slave trade for the period from 1650 to 1870, by decade, for eleven African regions of embarkation and seven American and European regions of arrival.