Year Percent 1950 28.18397 1955 29.04487 1960 29.40227 1965 25.15612 1970 22.34577 1975 22.9048 1980 25.26695 1985 28.6979 1990 30.57972 1995 30.55082 2000 30.81432 2005 31.82814 2010 33.94333 2015 35.09608 2020 34.32055 2025 32.04414 2030 30.08728 2035 28.83079 2040 28.63866 2045 28.66675 2050 27.53591 2055 26.01123 2060 24.83302 2065 24.30153 2070 24.10367 2075 23.80011 2080 23.24835 2085 22.61869 2090 22.16604 2095 21.95593 2100 21.88385