Which event in the early 20th century would change the data on this map?

a. the great migration
b. world war i
c. the dust bowl
d. the harlem renaissance

The correct answer is "A: The Great Migration".

The Great Migration was the relocation of more the 6 million African Americans from the rural and urban areas of Southeastern United States (the states of the former Confederacy) to urbanized locations in the northeast, midwest, and west of the country. This dramatically changed the population distribution of African Americans, as 90% of their total population lived in the Southeast prior to this policy but when it ended 50% would live in the designed areas for relocation.  

the answer here would be

demand is the need and oportunity to buy a given good or service.