Year Percent 1950 30.36347 1955 29.89855 1960 30.45998 1965 28.48229 1970 29.02599 1975 31.08948 1980 33.34131 1985 33.93548 1990 31.82863 1995 30.09889 2000 29.70839 2005 31.47695 2010 32.51292 2015 31.94051 2020 29.28171 2025 25.57862 2030 23.64135 2035 22.48845 2040 22.20947 2045 22.12181 2050 20.9776 2055 19.87593 2060 19.35644 2065 19.48315 2070 19.9435 2075 20.41277 2080 20.57192 2085 20.40993 2090 20.22548 2095 20.26993 2100 20.51691