r 1he determinants of the age and sex composition of the transatlantic slave 1 trade have long been a source of historical discussion. Contemporaries, including participants in the trade, analysed and debated the causes of the patterns they observed, as well as the consequences for the demographic, economic, and social developments both of Africa and of the Americas. The persistence of such debates over the course of three centuries makes further study of interest to economic historians, and the attempts to understand any seasonal variations and temporal fluctuations in the age and sex compositions provide some basis for increasing our knowledge of important changes on three continents. In bald terms, the explanations of the causes of the age and sex compositions divide into those emphasizing the demand factors generated in the New World, and those concentrating on the supply forces within Africa-either by the initial captors or by the dealers in slaves elsewhere in Africa. The New World arguments rest in part on letters of instruction to slave traders, but are buttressed by arguments suggesting that females had limited capability to handle field labour on the sugar plantations, to which most were sent, and implying a markedly lower value for female slaves than for male slaves there. Yet recent research on plantations has determined both that a higher percentage of females than of males were involved in field labour, and that price differentials were relatively small. Thus, scholars have begun anew to discuss another earlier argument, that the age and sex composition was influenced by conditions within Africa, and that the African captors and traders participated in setting the terms under which the trade took place. Both sides apparently agree that the proportion of males in the trade was high, and that of children low.2 One way to assess the two views is to study the fluctuations in age and sex among regions and over time. For while the letters quoted are often used to suggest a unique pattern of demand with a constant set of preferences (presumably irrespective of prices) for all regions over time, the degree to which variations occur suggests that