Year Percent 1950 32.93041 1955 30.69357 1960 28.79221 1965 26.44125 1970 27.96328 1975 31.82303 1980 37.25373 1985 40.96545 1990 42.06317 1995 38.25437 2000 33.11407 2005 31.26389 2010 29.78045 2015 27.97745 2020 26.67767 2025 25.38469 2030 24.15058 2035 22.53795 2040 21.23547 2045 20.49479 2050 20.22072 2055 19.9881 2060 19.75687 2065 19.49413 2070 19.16537 2075 18.88924 2080 18.71628 2085 18.62607 2090 18.54871 2095 18.43809 2100 18.27639