Year Percent 1950 29.05847 1955 30.62603 1960 33.28504 1965 31.72571 1970 32.43905 1975 30.35945 1980 30.17461 1985 27.77027 1990 29.83056 1995 28.18538 2000 28.36755 2005 28.4831 2010 28.12766 2015 28.32786 2020 28.58906 2025 29.25444 2030 30.25907 2035 31.32785 2040 32.09757 2045 32.58294 2050 32.84831 2055 32.88737 2060 32.77353 2065 32.47247 2070 31.97836 2075 31.34126 2080 30.65102 2085 29.98742 2090 29.39077 2095 28.84795 2100 28.32036