Answer:
Slave labor produced many of the consumer goods that were the basis of world trade between the 17th, and early 19th centuries.
Due to this, different industries got benefited by ¨cheap/free labor force¨ provoking on them an exponential fast-growing.
For this reason the slavery trade business was in high demand, thanks to the the labor force asked to opperate in different industry sectors, both business started to be more than profitable, and many governments of different parts of the world started to participate economically in the slavery trade.
The relationship between the two economies were directly proportional in a positive manner, being mutually benefited by their business, the industry taking advantage of the low costs provided by slavery labor force (low or not remmunerations to slaves), and the Slavery trade, getting a rounded business, with permanent demmand and transactions of slaves.
However, once the industrial revolution started to expand and evolve, provoked the usage of machines and automated systems in many (for not say all) factories and other industry sectors, this was a critical point in the ¨slavery usage¨, since some work required to be done by human force, was accomplished with new technology of the era, due this sporadically machines started to replace slaves, lowering the black people purchase demands.