Year Percent 1950 28.68872 1955 29.99163 1960 32.09863 1965 30.64633 1970 30.20466 1975 29.48866 1980 29.36858 1985 30.76612 1990 30.01037 1995 27.92532 2000 27.40868 2005 27.01166 2010 26.79868 2015 25.88583 2020 24.75851 2025 23.07586 2030 22.27259 2035 22.11644 2040 21.52191 2045 21.4362 2050 20.69077 2055 20.09709 2060 19.90927 2065 20.0385 2070 20.24542 2075 20.37247 2080 20.3327 2085 20.16997 2090 20.05382 2095 20.0928 2100 20.22747