Year Percent 1950 21.5409 1955 22.76669 1960 22.82538 1965 22.17666 1970 20.43687 1975 18.17994 1980 17.36813 1985 17.61211 1990 20.10952 1995 22.42147 2000 23.96423 2005 25.13107 2010 25.14927 2015 26.62441 2020 27.85311 2025 27.95952 2030 26.95176 2035 24.48634 2040 22.44527 2045 21.79658 2050 23.02427 2055 24.72087 2060 25.54293 2065 25.09913 2070 23.82645 2075 22.81077 2080 22.58589 2085 22.94498 2090 23.30647 2095 23.24989 2100 22.78704