Year % of total population 1960 31.4476760042077 1961 31.8238534724616 1962 32.2079337484831 1963 32.6278840087722 1964 33.0653474847151 1965 33.4732939446793 1966 33.8747058019102 1967 34.291252056258 1968 34.7173432866525 1969 35.0986439239995 1970 35.4522498626907 1971 35.8501443758216 1972 36.2856837533013 1973 36.7329463172608 1974 37.1678722558335 1975 37.5884161968221 1976 38.0000751480306 1977 38.4042720818844 1978 38.8052124948219 1979 39.2030129247625 1980 39.5961838445503 1981 39.9865002740913 1982 40.3692446031776 1983 40.7361744596988 1984 41.0798555824995 1985 41.3910383457922 1986 41.6643806167961 1987 41.9038768906423 1988 42.1143107094955 1989 42.2901405005076 1990 42.4226687452793 1991 42.5075371660256 1992 42.5435155179161 1993 42.5278806221756 1994 42.4539438612084 1995 42.3116517107501 1996 42.1006934636768 1997 41.8456085152983 1998 41.5630434638859 1999 41.2557338640814 2000 40.9316425943362 2001 40.5913867395281 2002 40.230611107136 2003 39.8512402989704 2004 39.4643815456745 2005 39.0792215602121 2006 38.6956505823993 2007 38.3204384382621 2008 37.9666470413968 2009 37.6588673462384 2010 37.4096563331882 2011 37.2097038081805 2012 37.0319675723646 2013 36.8644848549844 2014 36.7359981452628 2015 36.6597371380176 2016 36.630595595688 2017 36.6317784353959 2018 36.6293698732876 2019 36.5971021303642 2020 36.5273646684315 2021 36.4232081357299 2022 36.2841239560191 2023 36.089246897222