Year Percent 1950 16.08283 1955 16.43319 1960 16.73816 1965 17.01225 1970 17.41562 1975 18.40845 1980 19.13101 1985 18.2318 1990 17.03085 1995 16.39876 2000 14.93239 2005 14.15577 2010 13.99711 2015 14.30068 2020 13.46836 2025 12.55096 2030 11.64935 2035 10.89699 2040 10.29159 2045 9.77164 2050 9.23641 2055 8.67168 2060 8.13657 2065 7.67958 2070 7.30034 2075 6.98627 2080 6.71213 2085 6.44462 2090 6.20431 2095 6.004 2100 5.84185