Year Percent 1950 16.9308 1955 18.36882 1960 19.02308 1965 19.59772 1970 20.49422 1975 20.22712 1980 19.13235 1985 17.95885 1990 18.85849 1995 21.91693 2000 26.18547 2005 32.21438 2010 33.60617 2015 33.92015 2020 32.87054 2025 31.97774 2030 31.13527 2035 29.83896 2040 27.04728 2045 22.95874 2050 20.18535 2055 18.26294 2060 18.51014 2065 20.16895 2070 21.48844 2075 22.14674 2080 21.73162 2085 21.0212 2090 20.51903 2095 20.76957 2100 21.39018