Year Percent 1950 22.92451 1955 21.70661 1960 22.91901 1965 23.89439 1970 24.11209 1975 24.19146 1980 24.46089 1985 24.93898 1990 26.15315 1995 27.48719 2000 28.59224 2005 29.27658 2010 29.02481 2015 27.93684 2020 28.06159 2025 29.32641 2030 31.33949 2035 32.53663 2040 32.18947 2045 31.29259 2050 30.04028 2055 29.39358 2060 29.0531 2065 28.64747 2070 27.97818 2075 27.08146 2080 26.1178 2085 25.21105 2090 24.43125 2095 23.73684 2100 23.07867