What was the major reason that African Americans migrated to northern cities during and after World War I?

Driven from their homes by unsatisfactory economic opportunities and harsh segregationist laws, many Black Americans headed north, where they took advantage of the need for industrial workers that arose during the First World War.

hope if helpful if not then sorry

500 books can be produced by one man and a printing press within 5 months, while a copyist can only produce one in the same amount of time

which time period is this? or is this story fictional, i'm going to need more info to answer this question