Year Percent 1950 31.66564 1955 30.58998 1960 32.18003 1965 29.84266 1970 27.73194 1975 28.70269 1980 29.25447 1985 30.80799 1990 30.24119 1995 28.949 2000 28.19018 2005 29.84659 2010 31.9124 2015 33.12476 2020 31.55382 2025 28.01232 2030 23.30038 2035 21.0047 2040 20.45989 2045 20.56962 2050 19.83809 2055 18.60909 2060 17.88076 2065 17.85481 2070 18.3059 2075 18.94307 2080 19.37715 2085 19.46591 2090 19.39843 2095 19.44945 2100 19.70984