Year % of total population 1960 27.5341866409598 1961 27.5937829563482 1962 27.6547137726015 1963 27.7327148407901 1964 27.8250142513731 1965 27.8942869923337 1966 27.9300244049797 1967 27.9312860493285 1968 27.8985353343375 1969 27.8370032412182 1970 27.7445919553505 1971 27.6411459453718 1972 27.5493856710881 1973 27.4680800775374 1974 27.4174429845088 1975 27.4058726372514 1976 27.4141726280778 1977 27.4012168449954 1978 27.3419723323947 1979 27.2500118167978 1980 27.1251460008464 1981 26.9878452204192 1982 26.8621509424146 1983 26.7393638194552 1984 26.6161279545783 1985 26.5143958726513 1986 26.4122609294671 1987 26.2607203443718 1988 26.0927957496354 1989 25.9116007564507 1990 25.6651360878405 1991 25.3893474909213 1992 25.1497590790847 1993 24.9522700025774 1994 24.8081549995376 1995 24.7357323192968 1996 24.6892155554698 1997 24.6343298093199 1998 24.5657178463246 1999 24.4747500962957 2000 24.3594870276921 2001 24.2263943683903 2002 24.1079607953083 2003 23.9613135450173 2004 23.7530557809597 2005 23.5537644698907 2006 23.3545195741963 2007 23.1213219891965 2008 22.8737647909229 2009 22.6046123446394 2010 22.314982979141 2011 22.0293532541804 2012 21.7604469714554 2013 21.5227788046216 2014 21.3154821022086 2015 21.1415981021609 2016 20.9813736500979 2017 20.7676172100378 2018 20.4907760103319 2019 20.1696938973287 2020 19.7968321883977 2021 19.4366918209202 2022 19.0982161208381 2023 18.7461922401817