Year Percent 1950 4.27444 1955 3.90075 1960 3.31543 1965 2.61575 1970 2.84922 1975 2.73538 1980 2.26726 1985 2.16366 1990 2.22946 1995 2.4939 2000 2.97219 2005 3.60354 2010 3.42372 2015 4.07171 2020 6.14303 2025 8.45252 2030 12.05557 2035 15.65305 2040 18.17167 2045 19.85942 2050 20.51749 2055 20.95647 2060 21.99914 2065 22.62855 2070 23.51821 2075 24.73385 2080 26.05456 2085 26.98553 2090 27.70835 2095 28.4171 2100 29.17881