Year Percent 1950 27.25491 1955 26.8312 1960 26.36234 1965 25.18848 1970 24.59601 1975 25.14627 1980 25.94832 1985 26.86375 1990 27.83905 1995 28.38993 2000 29.37844 2005 30.64646 2010 31.91227 2015 33.34213 2020 34.13033 2025 34.24355 2030 33.49552 2035 31.89207 2040 30.28298 2045 28.78766 2050 27.63539 2055 26.76739 2060 25.74374 2065 24.66981 2070 23.68428 2075 22.8953 2080 22.30378 2085 21.86456 2090 21.50702 2095 21.19521 2100 20.92173