Year Percent 1950 30.5386 1955 30.2151 1960 29.61782 1965 29.31905 1970 29.50738 1975 29.69685 1980 33.34844 1985 33.05454 1990 33.06009 1995 32.35135 2000 22.98168 2005 24.02668 2010 25.27905 2015 24.20002 2020 27.54925 2025 28.63359 2030 30.42728 2035 31.78486 2040 31.55444 2045 32.10819 2050 32.33049 2055 32.29426 2060 32.14182 2065 31.66758 2070 30.96825 2075 30.25594 2080 29.59967 2085 28.99752 2090 28.37877 2095 27.67564 2100 26.92481