Year Percent 1950 32.43925 1955 31.48365 1960 30.43805 1965 29.51895 1970 29.17245 1975 29.42007 1980 28.76068 1985 28.653 1990 28.42697 1995 28.58004 2000 29.79416 2005 30.50628 2010 31.15282 2015 31.30344 2020 30.28597 2025 29.81547 2030 29.30194 2035 28.8276 2040 28.48717 2045 27.91182 2050 27.2737 2055 26.54282 2060 25.87494 2065 25.29305 2070 24.77576 2075 24.29209 2080 23.83009 2085 23.4008 2090 23.01298 2095 22.68794 2100 22.41585