Year Percent 1950 28.79765 1955 29.64444 1960 29.72501 1965 29.35052 1970 28.10173 1975 26.40366 1980 26.07824 1985 26.51618 1990 26.89787 1995 27.44171 2000 28.09451 2005 29.32993 2010 30.82339 2015 31.77833 2020 32.16722 2025 31.75606 2030 31.43786 2035 31.63042 2040 31.75269 2045 31.85822 2050 31.28912 2055 30.3397 2060 29.61903 2065 29.19609 2070 28.92015 2075 28.51379 2080 27.8914 2085 27.19831 2090 26.59539 2095 26.16151 2100 25.80609