 In 1923, the rate of inflation hit 3.25 × 106 percent per month (prices double every two days).Beginning on 20 November 1923, 1,000,000,000,000 old Marks were exchanged for 1 Rentenmark, so that 4.2 Rentenmarks were worth 1 US dollar, exactly the same rate the Mark had in 1914.With the German invasion in April 1941, there was an abrupt increase in prices.