Economic historians usually consider the catalyst of the Great Depression to be the sudden devastating collapse of U.S. stock market prices, starting on October 24, 1929. However, some dispute this conclusion and see the stock crash as a symptom, rather than a cause, of the Great Depression.
Even after the Wall Street Crash of 1929 optimism persisted for some time. John D. Rockefeller said "These are days when many are discouraged. In the 93 years of my life, depressions have come and gone. Prosperity has always returned and will again." The stock market turned upward in early 1930, returning to early 1929 levels by April. This was still almost 30% below the peak of September 1929.
Together, government and business spent more in the first half of 1930 than in the corresponding period of the previous year. On the other hand, consumers, many of whom had suffered severe losses in the stock market the previous year, cut back their expenditures by 10%. In addition, beginning in the mid-1930s, a severe drought ravaged the agricultural heartland of the U.S.
By mid-1930, interest rates had dropped to low levels, but expected deflation and the continuing reluctance of people to borrow meant that consumer spending and investment were depressed. By May 1930, automobile sales had declined to below the levels of 1928. Prices, in general, began to decline, although wages held steady in 1930. Then a deflationary spiral started in 1931. Farmers faced a worse outlook; declining crop prices and a Great Plains drought crippled their economic outlook. At its peak, the Great Depression saw nearly 10% of all Great Plains farms change hands despite federal assistance.
The decline in the U.S. economy was the factor that pulled down most other countries at first; then, internal weaknesses or strengths in each country made conditions worse or better. Frantic attempts to shore up the economies of individual nations through protectionist policies, such as the 1930 U.S. Smoot–Hawley Tariff Act and retaliatory tariffs in other countries, exacerbated the collapse in global trade. By 1933, the economic decline had pushed world trade to one third of its level just four years earlier.
Change in economic indicators 1929–32