Year Percent 1950 30.86657 1955 30.13146 1960 32.21933 1965 30.20976 1970 28.63558 1975 28.54222 1980 27.77625 1985 27.29843 1990 28.04095 1995 27.83923 2000 28.08477 2005 29.38184 2010 27.84562 2015 25.76588 2020 23.48631 2025 22.65014 2030 21.30094 2035 21.01717 2040 20.86054 2045 20.69112 2050 20.23761 2055 20.08675 2060 20.11787 2065 20.2922 2070 20.51577 2075 20.66565 2080 20.66154 2085 20.58368 2090 20.53454 2095 20.52758 2100 20.54014