Year Percent 1950 3.84925 1955 3.85298 1960 3.80365 1965 3.79251 1970 3.79071 1975 3.76795 1980 3.78778 1985 3.80325 1990 3.86976 1995 4.04113 2000 4.34145 2005 3.96536 2010 3.97834 2015 3.95193 2020 3.92071 2025 3.90995 2030 4.02037 2035 4.25221 2040 4.86465 2045 6.29876 2050 8.47056 2055 10.62552 2060 12.31558 2065 13.69009 2070 15.18983 2075 16.83795 2080 18.57377 2085 20.18069 2090 21.61456 2095 22.93522 2100 24.20734