Jazz is a music genre that originated in the African-American communities in the early 20th century. The Jazz age occurred during 1920 - 1930 i.e, started post-World War 1 movement and ended with the Great Depression in 1929. It was the age in which jazz music and dance emerged.
The multiplier effect means that "An effect in economics in which an increase in spending produces an increase in national income and consumption greater than the initial amount spent."