Year Percent 1950 30.64597 1955 29.85343 1960 34.51896 1965 33.46402 1970 30.64029 1975 31.96722 1980 30.5185 1985 31.7958 1990 31.29843 1995 30.38927 2000 30.37946 2005 31.61942 2010 33.21521 2015 32.55267 2020 29.96395 2025 26.25274 2030 23.89056 2035 23.86892 2040 25.10906 2045 26.20165 2050 25.48023 2055 24.30276 2060 23.56804 2065 23.60408 2070 24.1829 2075 24.69737 2080 24.62393 2085 23.99108 2090 23.28527 2095 22.94293 2100 22.99439