Year Percent 1950 21.72866 1955 22.65363 1960 22.49204 1965 22.62807 1970 23.01994 1975 23.42463 1980 23.12088 1985 22.66844 1990 22.53676 1995 22.51915 2000 24.47026 2005 26.49184 2010 28.02713 2015 30.22991 2020 31.48832 2025 30.58635 2030 28.32424 2035 25.22622 2040 22.04205 2045 20.98575 2050 21.58711 2055 22.16653 2060 22.69996 2065 22.43185 2070 21.52687 2075 21.17014 2080 21.21451 2085 21.52871 2090 21.7822 2095 21.74432 2100 21.41566