Year Percent 1950 31.22994 1955 29.39266 1960 28.05743 1965 26.41505 1970 28.26559 1975 32.03309 1980 37.16059 1985 40.7104 1990 42.24898 1995 38.41845 2000 33.48933 2005 31.64894 2010 30.16801 2015 28.08039 2020 26.36436 2025 24.76672 2030 23.48752 2035 21.83111 2040 20.5135 2045 19.71894 2050 19.36494 2055 19.13218 2060 18.92237 2065 18.70011 2070 18.42339 2075 18.19906 2080 18.06956 2085 18.00635 2090 17.94542 2095 17.85053 2100 17.70721