went from 25% to 63% in 1932 and to 79% in 1936, while the bottom rate increased over tenfold, from .375% in 1929 to 4% in 1932. The concurrent massive drought resulted in the U.S. Dust Bowl. The Austrian School aruged that the Great Depression was the result of a credit bust. Alan Greenspan wrote that the bank failures of the 1930s were sparked by Great Britain dropping the gold standard in 1931. This act "tore asunder" any remaining confidence in the banking system. Financial historian Niall Ferguson wrote that what made the Great Depression truly 'great' was the European banking crisis of 1931. According to Federal Reserve Chairman Marriner Eccles, the root cause was the concentration of wealth resulting in a stagnating or decreasing standard of living for the poor and middle class. These classes went into debt, producing the credit explosion of the 1920s. Eventually, the debt load grew too heavy, resulting in the massive defaults and financial panics of the 1930s. Bretton Woods Under the Bretton Woods international monetary agreement of 1944, the gold standard was kept without domestic convertibility. The role of gold was severely constrained, as other countries' currencies were fixed in terms of the dollar. Many countries kept reserves in gold and settled accounts in gold. Still, they preferred to settle balances with other currencies, with the US dollar becoming the favorite. The International Monetary Fund was established to help with the exchange process and assist nations in maintaining fixed rates. Within Bretton Woods adjustment was cushioned through credits that helped countries avoid deflation. Under the old standard, a country with an overvalued currency would lose gold and experience deflation until the currency was again valued correctly. Most countries defined their currencies in terms of dollars, but some countries imposed trading restrictions to protect reserves and exchange rates. Therefore, most countries' currencies were still basically inconvertible. In the late 1950s, the exchange restrictions were dropped and gold became an important element in international financial settlements. After the Second World War, a system similar to a gold standard and sometimes described as a "gold exchange standard" was established by the Bretton Woods Agreements. Under this system, many countries fixed their exchange rates relative to the U.S. dollar and central banks could exchange dollar holdings into gold at the official exchange rate of per ounce; this option was not available to firms or individuals. All currencies