Year Percent 1950 16.74303 1955 16.85569 1960 17.12764 1965 16.6704 1970 15.58057 1975 15.07274 1980 16.66329 1985 18.21555 1990 20.30804 1995 23.58428 2000 27.71936 2005 29.79427 2010 31.14872 2015 29.94367 2020 27.34273 2025 24.63979 2030 23.20962 2035 23.07793 2040 24.11734 2045 24.91161 2050 25.19017 2055 25.0721 2060 24.94852 2065 24.81023 2070 24.88404 2075 24.58756 2080 24.10716 2085 23.71039 2090 23.46497 2095 23.32067 2100 23.20045