If the cause was, "the cotton gin cleaned cotton much faster," what was the effect?

The effect was that way before cotton gins were invented, slaves needed to clean cottons by hand, and a cotton gin cleans a cotton perfectly and much more faster than a slave cleaning the cotton and the cotton gin could clean more cottons at once than a slave cleaning cottons one by one.

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.

what are the reasons