Year Percent 1950 28.45498 1955 27.93369 1960 29.43187 1965 27.03687 1970 28.09614 1975 29.25629 1980 30.70234 1985 32.06998 1990 31.17252 1995 30.23826 2000 28.97082 2005 27.78412 2010 26.57097 2015 25.12948 2020 24.7015 2025 24.38588 2030 24.35648 2035 24.4321 2040 24.25392 2045 23.89466 2050 23.53173 2055 23.4034 2060 23.42567 2065 23.43353 2070 23.31152 2075 23.04626 2080 22.74063 2085 22.5086 2090 22.36888 2095 22.27179 2100 22.14976