Year Percent 1950 29.27889 1955 27.89967 1960 26.01678 1965 25.19951 1970 25.70843 1975 27.35345 1980 29.82163 1985 31.72689 1990 31.93004 1995 30.90405 2000 29.58958 2005 28.23621 2010 28.23729 2015 27.86171 2020 27.09567 2025 25.99889 2030 25.46878 2035 24.46696 2040 24.15628 2045 23.94298 2050 23.31468 2055 22.68747 2060 22.21989 2065 21.83498 2070 21.56297 2075 21.34462 2080 21.11461 2085 20.8387 2090 20.56955 2095 20.35581 2100 20.19234