Cheaper than wallpaper. Banknotes decorate the walls of a German apartment. In order to pay the large costs of WWI, Germany suspended the convertibility of its currency into gold when that war broke out. The German Kaiser and Parliament decided without opposition to fund the war entirely by borrowing. The result was that the exchange rate of the Mark against the U.S. dollar fell steadily throughout the war from 4.2 to 8.91 Marks per dollar. The Treaty of Versailles, further accelerated the decline in the value of the Mark, so that by the end of 1919 more than 6.7 paper Marks were required to buy one U.S. dollar. The hyperinflation in the Weimar Republic was a three year period between June 1921 and January 1924. By November 1923, the U.S. dollar was worth 4,210,500,000,000 German marks.