Year Percent 1950 19.94769 1955 18.68719 1960 17.06548 1965 16.54622 1970 15.92667 1975 15.19718 1980 14.88521 1985 13.85102 1990 12.13044 1995 14.63698 2000 17.57341 2005 21.5316 2010 25.21197 2015 28.76192 2020 29.15245 2025 28.90447 2030 27.94001 2035 26.29248 2040 23.89265 2045 21.65758 2050 21.34454 2055 22.83381 2060 24.72496 2065 25.85056 2070 25.57921 2075 24.23098 2080 23.55664 2085 23.74315 2090 24.09559 2095 24.04243 2100 23.54033