Between 1919 and 1920:

• America's gross national product (GNP) grew from $78 billion to $103 billion.
• The number of households with a radio rose from 60,000 to 10 million.
• The number of people filing income tax returns for earnings of more than $1 million a year rose from 65 to 513.
• The number of airline passengers grew from less than 6000 in 1926, to approximately 173,000 in 1929.

Five causes of the boom

1. solationism- the republican government under President Harding (1921-3) and President Coolidge (1923-9) kept out of foreign affairs, and limited foreign competition by imposing high import tariffs.
2. Technology- especially in the electrical, chemicals…