During the first World War, American business interests flourished. Weapons and food were sold to the Allies and there was a great increase in exports to world markets at that time when an exhausted Europe could offer little competition in world trade. All American banks, in order to encourage the agricultural and industrial production opened credit to anybody.

The mania to "get rich quick"spread among the whole population. One way was to buy the shares of money to be able to take part in the gamble, without thinking about the true value of what they were buying. The Europe started again to produce enough for its necessity so that some commercial prohibition impeded the American business. The over production had hed to a fall-off in trade and company profits, the warkers were laid off.

The banks called on their clients to sell their shares but there were no buyers, this produced panic and on October 24, 1929 there was "the Wall Street Crash".

America was plunged in to the Great Depression. The president Hebert Hoover could take no drastic action and his democratic opponent, Franklin D. Roosevelt argued that the depression had been aggravated by Republican policies. American bankers and financiers lent vast sums to France, Britain and Germany. Germany had to refund war damages to the Allies but Hoover didn’t understand that the payment of debts was conneted to a favourable commercial balance of the Europeans countries. In 1933, Roosevelt was elected President after having promised the American people a "New Deal" . He wanted  to give relief to the suffering brought on by the depression and helped firms and businessmen to get back to work providing them with financial aids. In agriculture the Congress passed an act providing that the government should give money to formers who would be devote to Roosevelt’s political party, the new Act likewise provided loaris on surplus craps, insurance for wheat.

Soon, prices of agricultural commodities rose and economic stability for farmers began to seem possible.

The federal government spent thousands of million of dollars on rerlief of the unemployed, on public work and the conservation of national resources. The economy slowly began to improve, but by the end of 1937 business began to flounder once again since the first War World. Great Britain was one of the countries that less suffered the "Wall Street Crash" because it had got the resources coming from  the biggest colonial empire of the world and colonies formed a market for the British manufact. This privilege was the cause of weakness because Great Britain did not invest capitals for the renovation causing the technical backwardness of the old base industry to favour of Germany, Japan and United States.

In spite of the big colonial empire,  recession struck Great Britain causing a decrease of 30% of the production and three million of unemployment in 1930. James Ramsay Mac Donald's labour government   acted a deflationary politics in order to avoid the devalutation of the pound (whose conversion in gold was stopped in 1931) and replaced the free commerce with the protectionism.