The document analyzes the relationship between stock market performance and economic growth in the U.S. from 1980-2011. It finds a strong positive correlation between changes in the Dow Jones Industrial Average and nominal GDP. Regression analysis shows stock market fluctuations explained about 87% of the variation in GDP. The results suggest stock prices can influence economic activity by affecting business confidence, financing, and household wealth. Therefore, large declines in stock prices may precede and prolong economic downturns.