Dutch research into the slave trade and its importance to the Dutch economy has often limited itself to investigating the financial success of slave trading companies, calculating the success of slaving by its profit rates. The central argument made in this article is that grossmargin is a better indicator for the importance of the slave trade to the Dutch Republic. Even if a slave trading company did not make a net profit on a voyage, such a voyage led to extra activities such as shipbuilding or the production of trade goods. This article provides a reconstruction of this gross margin for the entire period that the Dutch were engaged in the trans-Atlantic slave trade by combining the most recent data on the size of the slave trade (including illicit trade) with data on both African and American price data of slaves.