The outbreak of World War I caused France to leave the gold standard of the LMU. The war severely undermined the franc's strength: war expenditure, inflation and postwar reconstruction, financed partly by printing ever more money, reduced the franc's purchasing power by 70% between 1915 and 1920. After a brief appreciation of the franc during the Depression of 1920–1921, it depreciated a further 43% between 1922 and a balancing of the budget in 1926. This devaluation was aggravated by the insistence of the Republican U.S. federal government and World War Foreign Debts Commission that France's war debts be repaid within 25 years at a minimal 4.25 percent interest per year. The currency devaluation contributed to French demands for high reparations payments from Germany. After a brief return to the gold standard between 1928 and 1936, the currency was allowed to resume its slide, until in 1959 it was worth less than 2.5% of its 1934 value.