Year Percent 1950 17.06117 1955 17.20778 1960 17.86318 1965 18.41873 1970 18.51041 1975 18.80713 1980 18.45761 1985 17.85479 1990 16.59292 1995 15.52737 2000 15.26616 2005 13.7421 2010 13.14503 2015 13.37031 2020 12.91454 2025 12.08541 2030 11.23128 2035 10.60455 2040 10.08073 2045 9.56588 2050 9.01239 2055 8.49246 2060 8.02412 2065 7.60355 2070 7.26659 2075 6.97416 2080 6.70389 2085 6.4645 2090 6.24882 2095 6.06752 2100 5.91278