Year Percent 1950 31.59368 1955 30.69205 1960 32.05903 1965 29.74256 1970 27.54809 1975 28.74097 1980 29.87131 1985 31.6203 1990 30.95942 1995 29.64215 2000 29.04711 2005 31.09597 2010 33.40182 2015 34.95214 2020 33.47745 2025 29.82485 2030 24.954 2035 22.67877 2040 22.19988 2045 22.29195 2050 21.50499 2055 20.15408 2060 19.39305 2065 19.38316 2070 19.85499 2075 20.46957 2080 20.80312 2085 20.73789 2090 20.52601 2095 20.48072 2100 20.68002