Year Percent 1950 27.36477 1955 28.82681 1960 27.10943 1965 25.36944 1970 24.95142 1975 24.53875 1980 25.38197 1985 25.50479 1990 25.30102 1995 25.54116 2000 26.45132 2005 28.4655 2010 29.35641 2015 29.79315 2020 28.91179 2025 28.0494 2030 26.78658 2035 26.15367 2040 25.97098 2045 25.19253 2050 24.59795 2055 24.22332 2060 24.05329 2065 24.0977 2070 24.25459 2075 24.2605 2080 23.99642 2085 23.68014 2090 23.42479 2095 23.25339 2100 23.1373