Year Percent 1950 29.858 1955 26.73061 1960 23.5153 1965 21.2755 1970 22.17393 1975 26.38741 1980 29.81673 1985 34.55948 1990 36.27359 1995 35.3617 2000 31.48933 2005 29.52421 2010 27.74592 2015 26.09907 2020 25.06711 2025 24.23343 2030 23.86504 2035 23.57758 2040 23.4909 2045 23.28761 2050 23.13974 2055 22.98441 2060 22.86143 2065 22.75369 2070 22.64803 2075 22.52732 2080 22.37161 2085 22.20431 2090 22.04958 2095 21.92208 2100 21.81902