Year Percent 1950 3.89515 1955 3.87329 1960 3.93185 1965 4.01038 1970 3.96916 1975 4.06266 1980 4.20771 1985 4.50813 1990 5.25515 1995 5.46098 2000 5.58434 2005 5.61169 2010 5.66337 2015 6.09665 2020 6.49566 2025 6.87535 2030 7.45734 2035 8.38254 2040 9.76519 2045 11.56796 2050 13.55647 2055 15.9364 2060 18.45137 2065 20.95975 2070 23.01358 2075 24.89161 2080 26.68045 2085 28.33052 2090 29.80599 2095 31.11279 2100 32.27554