How had argiculture, foreign trade, and credit of american economy shown a weakness before the depression

The US economy had experienced rapid economic growth and financial excess in the late 1920s, and initially the economic downturn was seen as simply part of the boom-bust-boom cycle. Unexpectedly, however, output continued to fall for three and a half years, by which time half of the population was in desperate circumstances (map1). It also became clear that there had been serious over-production in agriculture, leading to falling prices and a rising debt among farmers. At the same time there was a major banking crisis, including the "Wall Street Crash" in October 1929. The situation was aggravated by serious policy mistakes of the Federal Reserve Board, which led to a fall in money supply and further contraction of the economy. 

1. Stock Market Crash of 1929 
Many believe erroneously that the stock market crash that occurred on Black Tuesday, October 29, 1929 is one and the same with the Great Depression. In fact, it was one of the major causes that led to the Great Depression. Two months after the original crash in October, stockholders had lost more than $40 billion dollars. Even though the stock market began to regain some of its losses, by the end of 1930, it just was not enough and America truly entered what is called the Great Depression. 

2. Bank Failures 
Throughout the 1930s over 9,000 banks failed. Bank deposits were uninsured and thus as banks failed people simply lost their savings. Surviving banks, unsure of the economic situation and concerned for their own survival, stopped being as willing to create new loans. This exacerbated the situation leading to less and less expenditures. 

3. Reduction in Purchasing Across the Board 
With the stock market crash and the fears of further economic woes, individuals from all classes stopped purchasing items. This then led to a reduction in the number of items produced and thus a reduction in the workforce. As people lost their jobs, they were unable to keep up with paying for items they had bought through installment plans and their items were repossessed. More and more inventory began to accumulate. The unemployment rate rose above 25% which meant, of course, even less spending to help alleviate the economic situation. 

4. American Economic Policy with Europe 
As businesses began failing, the government created the Smoot-Hawley Tariff in 1930 to help protect American companies. This charged a high tax for imports thereby leading to less trade between America and foreign countries along with some economic retaliation. 

5. Drought Conditions 
While not a direct cause of the Great Depression, the drought that occurred in the Mississippi Valley in 1930 was of such proportions that many could not even pay their taxes or other debts and had to sell their farms for no profit to themselves. The area was nicknamed "The Dust Bowl." This was the topic of John Steinbeck's The Grapes of Wrath.

following type of cultural development caused people to want and buy new products on the market :

industrialization