Internal causes: buying of stocks on credit, consumer use of credit, farming overproduction, industrial overproduction, tariffs on global goods.
External causes: loss of global market, policy of circular loans to Germany.
Weighing it out, the over extension of credit and ignorant investments of Americans contributed greatly to the boom and bust leading to the Great Depression. The industrial and farming sectors also did not adjust their production numbers for a crashing global market. They created surplus and therefore had to fire people from their jobs which meant they could pay their credit debt, which then led to crashing of banks and the stock market.
