Compare and contrast the "boom" industries and the "sick" industries of the 1920s.
The 1920s experienced a rapid expansion in manufacturing with the advent of specialized labor (many workers doing simple repetitive jobs in the most efficient manner possible) and the assembly line. This made consumer goods such as radios and cars much more affordable for ordinary Americans, and expanded the original business model for sales of these goods.
With the addition of installment payments or credit, this led to a sustained, seemingly endless expansion of the marketplace and sales along with the associated stock price of those companies.
Agriculture didn't see a corresponding boom, nor did textile factories in New England, which both overproduced and the corresponding drop in prices created more than a decade of hardship in these areas.