Year Percent 1950 17.32021 1955 18.34507 1960 18.7156 1965 17.55202 1970 16.65439 1975 16.2696 1980 17.15841 1985 18.19929 1990 19.06231 1995 20.87757 2000 22.2054 2005 26.39082 2010 30.35143 2015 32.51821 2020 31.98583 2025 28.75369 2030 26.68845 2035 24.54656 2040 24.73957 2045 24.43496 2050 22.75933 2055 22.2934 2060 22.15188 2065 22.52552 2070 22.94803 2075 22.64654 2080 22.23996 2085 21.94251 2090 21.89585 2095 21.97447 2100 22.0057