Share of child slaves along select routes 1636-1867

Throughout most of the transatlantic slave trade, slave children were generally viewed as a financial burden on plantation owners in the Americas; although they too were forced to work, their output usually did not return the initial investment or maintenance costs (food, lodge, etc.) until they were in their teens. Prior to the 19^th century, plantation owners in the Americas preferred simply to replace adult slaves with new adult slaves, for an immediate return on their investment. However, following the British and (to a lesser extent) American enforcement of the slave trade's abolition in 1807-08, slave owners in the Americas began to rely increasingly on child slavery as a long-term solution to the diminishing slave trade.

For slave traders, children were usually the last to be purchased from slavers in Africa, often to meet (usually exceed) the capacity of the slave ships. Because of their lower value and importance, it is thought that some traders drastically undercounted the number of children (particularly infants) who boarded each ship. In particular, records from the Portuguese routes to Brazil prior to 1811 show some of the lowest figures from these samples, with two routes recording around one percent of all slaves as being under the age of seven. With the increasing importance of children in the transatlantic slave trade, it is thought that records became more accurate in the 19^th century, which explains the jump to around forty percent in journeys to Cuba and Brazil in these years.