Answer:
Mass production and easy credit.
Explanation:
Before the 1920s, cars were very expensive. In the 1920s, the industry turned to mass production because it was really more profitable to produce millions of financially affordable cars than producing a few thousands for the rich people. Technology advances such as the assembly line and design innovations, plus sales strategy and easy credit, made this possible. In 1918, only 1 in 13 families owned a car. In 1929, 4 out of 5 families had a car.
