How did U. S. Economic policies contribute to the change in the gross national product from 1927 to 1934?

The years prior to 1929 were affluent and optimistic; there was a general belief that stock markets would continue to grow indefinitely, and speculation was rampant. Nevertheless, this was not the case, and a great economic crash occurred in October 29, 1929, also known as Black Tuesday. Billions of dollars were lost. It marked the beginning of the great economic downfall known as "The Great Depression", that lasted until 1939. The president of the United States, Franklin D. Roosevelt, created multiple agencies and promoted public policies to address the problem of poverty and unemployment. To sum up, there was an initial era of total deregulation (the 20s), followed by a great economic depression, which led to interventionist policies and the final recovery of the American economy.