Year Percent 1950 5.06177 1955 4.94538 1960 4.98248 1965 5.05027 1970 5.13179 1975 5.18545 1980 5.18538 1985 5.06563 1990 4.94002 1995 4.52389 2000 4.18584 2005 4.13131 2010 4.14703 2015 4.13989 2020 4.1772 2025 4.34974 2030 4.68076 2035 5.22545 2040 5.91341 2045 6.72516 2050 7.55156 2055 8.45166 2060 9.54102 2065 10.82884 2070 12.27255 2075 13.62241 2080 14.90944 2085 16.14196 2090 17.32466 2095 18.44636 2100 19.50254