Year Percent 1950 4.84501 1955 4.64361 1960 4.57074 1965 4.53553 1970 4.55367 1975 4.57725 1980 4.56861 1985 4.50427 1990 4.63319 1995 4.42778 2000 4.23333 2005 4.04527 2010 3.90491 2015 4.23272 2020 4.48335 2025 4.72155 2030 4.95221 2035 5.26017 2040 5.66288 2045 6.09031 2050 6.59455 2055 7.14809 2060 7.78875 2065 8.61849 2070 9.63441 2075 10.6824 2080 11.74877 2085 12.85975 2090 14.02663 2095 15.23781 2100 16.47488