Year Percent 1950 26.77941 1955 26.1226 1960 25.79914 1965 25.80423 1970 25.65497 1975 26.91138 1980 28.29461 1985 29.56706 1990 30.9691 1995 31.51457 2000 31.61182 2005 31.59476 2010 31.75715 2015 31.68502 2020 31.43346 2025 30.78368 2030 30.04234 2035 29.35589 2040 28.67745 2045 28.1064 2050 27.35822 2055 26.5158 2060 25.68353 2065 24.9067 2070 24.19409 2075 23.53524 2080 22.93123 2085 22.39196 2090 21.91837 2095 21.51716 2100 21.17907