Year Percent 1950 13.32979 1955 15.37383 1960 15.27346 1965 15.24443 1970 15.66001 1975 14.17139 1980 15.75483 1985 18.20275 1990 17.19968 1995 16.73769 2000 17.06164 2005 17.19955 2010 17.04581 2015 16.51385 2020 15.82563 2025 15.18234 2030 14.31749 2035 13.36296 2040 12.45945 2045 11.6766 2050 10.92605 2055 10.23091 2060 9.57853 2065 8.96255 2070 8.41171 2075 7.9041 2080 7.46974 2085 7.08278 2090 6.74074 2095 6.43681 2100 6.16594