How did the imperial powers use trade as a mechanism for control

It demanded cheap labor, and more workers they have the more control they had.

Explanation:

Imperial governments, and/or private companies under those governments, sought ways to maximize profits. Economic expansion demanded cheap labor, access to or control of markets to sell or buy products, and natural resources such as precious metals and land; governments have met these demands by hook (tribute) or by crook (plunder). After the advent of the Industrial Revolution, dependent colonies often provided to European factories and markets the raw materials they needed to manufacture products.

u.s.a

china

india

and

japan

the second significant cause of the great migration was the desire of black southerners to escape segregation, known euphemistically as jim crow. rural african american southerners believed that segregation - and racism and prejudice against blacks - was significantly less intense in the north.