Answer: The Industrial Revolution.
Step-by-step explanation:
The industrial revolution fundamentally changed everyday life. People began to leave the rural areas of the country en masse and move to the cities. Cities are becoming centers of life and places where industrial plants are installed. A large number of people are moving to cities for better opportunities. The industrial revolution had its phases in the twentieth century as well, so that process continued in that period. Thus, the economic factors of this phenomenon are in the background.