Year Percent 1950 14.96172 1955 17.90364 1960 17.89627 1965 17.52002 1970 16.95171 1975 16.68108 1980 17.8063 1985 18.97364 1990 16.56235 1995 12.5204 2000 9.64883 2005 7.83048 2010 8.57015 2015 8.60096 2020 7.33059 2025 5.91775 2030 4.94167 2035 4.67108 2040 4.84198 2045 4.97987 2050 4.78383 2055 4.37511 2060 4.03588 2065 3.95552 2070 4.1143 2075 4.3389 2080 4.43936 2085 4.37483 2090 4.24291 2095 4.18822 2100 4.25846