Year Percent 1950 29.2811 1955 28.95187 1960 28.29742 1965 28.13781 1970 27.99937 1975 28.45396 1980 28.3115 1985 27.46961 1990 27.5042 1995 28.16519 2000 31.7108 2005 35.73148 2010 38.45519 2015 40.08257 2020 41.97783 2025 42.27193 2030 41.02408 2035 38.1868 2040 35.75295 2045 34.38546 2050 33.18647 2055 32.35824 2060 31.64005 2065 31.06329 2070 30.59003 2075 30.17303 2080 29.76779 2085 29.2885 2090 28.74437 2095 28.13092 2100 27.48636