The Weimar Republic suffered from hyperinflation between 1921 and 1923. In 1918 the exchange rate had been 5.21 Mark to the US Dollar. By December 1923 the dollar was worth 4.2 trillion Mark (4,200,000,000,000 M). Before 1921, the postal rates for letters under 20g were 40 Pfennig for domestic mail and 80 Pfennig for foreign mail. By the end of 1923, these had to risen to 50 billion Mark and 300 billion Mark, respectively. At the peak of the inflation, bank notes with face values of up to 100 trillion Mark were in circulation and postage stamps in denominations up to 50 billion Mark were issued.