The Great Depression was the worst economic disaster in U.S. history in terms of declines in real GDP and increases in the unemployment rate. Use the data in the following table to calculate the percentage decline in real GDP between 1929 and 1933.

Year Nominal GDP Billions of Dollars GDP Price Deflator (yr 2000 = 100)
1929 103.6 11.9
1933 56.4 8.9

Real GDP changed by _____% over the 4 year period between 1929 and 1933. Enter a percentage value rounded to one decimal place. Include a minus sign if necessary.