Year Percent 1950 15.8296 1955 15.90789 1960 15.88989 1965 15.6323 1970 15.40676 1975 14.96021 1980 14.49501 1985 14.40611 1990 14.41251 1995 15.35491 2000 16.29241 2005 16.89836 2010 17.37449 2015 18.38418 2020 19.63528 2025 21.56859 2030 23.58911 2035 25.00233 2040 25.68236 2045 25.65098 2050 25.58657 2055 26.01761 2060 26.58977 2065 27.09823 2070 27.28863 2075 27.08694 2080 26.85933 2085 26.69979 2090 26.58193 2095 26.4343 2100 26.20258