What conditions made a consumer economy possible in the 1920s?

First of all, in the 1920s we had a large and vibrant middle class for the first time in our nation's history.  Factory jobs like in Henry Ford's auto plant paid well, and the number of factories exploded for all kinds of manufactured goods.  Ford's assembly line methods made these items cheaper and more affordable for the middle class, so sales of all items was very high.  This was your consumer economy.

 Another factor that led to this economy was financing called installment plans, where for the first time, consumers made monthly payments for more expensive items.  Now they could afford homes, cars, radios, washing machines and record players.  The availability of these items, installment payment plans and middle class jobs are together what led to the consumer economy of the 1920s.