Year Percent 1950 3.92585 1955 3.61346 1960 3.48086 1965 3.47108 1970 3.5201 1975 3.62224 1980 3.64064 1985 3.94934 1990 4.27512 1995 4.55855 2000 4.46295 2005 4.639 2010 4.968 2015 5.60132 2020 6.06027 2025 7.41821 2030 8.63722 2035 9.74895 2040 9.6961 2045 13.48663 2050 15.03167 2055 17.71715 2060 19.57136 2065 20.63695 2070 22.14638 2075 23.81025 2080 25.49065 2085 26.94898 2090 28.22502 2095 29.48242 2100 30.74785