Year Percent 1950 25.69766 1955 26.72593 1960 24.24826 1965 25.54711 1970 25.47945 1975 24.67582 1980 25.9243 1985 25.05549 1990 25.11066 1995 26.69718 2000 27.87246 2005 27.13098 2010 27.60259 2015 26.97477 2020 27.94422 2025 28.7671 2030 28.66077 2035 27.91613 2040 25.67794 2045 24.85826 2050 24.42881 2055 23.24309 2060 23.1616 2065 23.28125 2070 23.20384 2075 23.27268 2080 23.1994 2085 23.07238 2090 22.92784 2095 22.8615 2100 22.82022