Year Percent 1950 4.62751 1955 4.22319 1960 4.07761 1965 4.05564 1970 4.11308 1975 4.23935 1980 4.40705 1985 4.57288 1990 4.85693 1995 4.91646 2000 5.01979 2005 4.90333 2010 4.76122 2015 4.83232 2020 5.01611 2025 5.28575 2030 5.65083 2035 6.15427 2040 6.77141 2045 7.50472 2050 8.22316 2055 8.94517 2060 9.94245 2065 11.16441 2070 12.43579 2075 13.68237 2080 14.95813 2085 16.28212 2090 17.64933 2095 19.04485 2100 20.45829