Year Percent 1950 4.34474 1955 4.26994 1960 4.45369 1965 2.55507 1970 3.86068 1975 3.50863 1980 3.49053 1985 3.6738 1990 3.71483 1995 3.86465 2000 3.83561 2005 3.43726 2010 3.54608 2015 4.12872 2020 5.35751 2025 7.1578 2030 9.20783 2035 11.62204 2040 14.26864 2045 15.90801 2050 17.38922 2055 19.55193 2060 23.0868 2065 26.66893 2070 29.69137 2075 32.66864 2080 34.97939 2085 36.20142 2090 36.7162 2095 37.04722 2100 37.06204