The one with the most companies and the most shares traded is not even in New York. In fact, America's biggest stock exchange isn't anywhere , really. It has no building, no trading floor. You can't visit it. That's because it's an electronic exchange, where stocks are bought and sold by computer.
Economists study the way people produce, distribute, and consume goods and services.
The stock market broke down in 1929, leading to the Great Depression of the 1930s. It stumbled again in 1987, but was quickly repaired. What economists mean is that the stock market is a good way to create goods and services. Companies raise money by selling stock. They use the money to hire people or buy materials to sell insurance or make widgets.