Year % of total population 1960 47.133 1961 46.337 1962 45.541 1963 44.747 1964 43.955 1965 43.168 1966 42.383 1967 41.602 1968 40.825 1969 40.054 1970 39.287 1971 38.567 1972 37.878 1973 37.195 1974 36.516 1975 35.843 1976 35.17400000000001 1977 34.513000000000005 1978 33.857 1979 33.31399999999999 1980 32.905 1981 32.56 1982 32.278000000000006 1983 31.997 1984 31.717 1985 31.439999999999998 1986 31.218000000000004 1987 31.052999999999997 1988 30.888000000000005 1989 30.799999999999997 1990 30.75 1991 30.799000000000007 1992 31.147999999999996 1993 31.200999999999993 1994 31.099000000000004 1995 31.25 1996 31.349999999999994 1997 31.400000000000006 1998 31.549000000000007 1999 31.78 2000 31.933000000000007 2001 32.05 2002 32.150000000000006 2003 32.2 2004 32.099999999999994 2005 32 2006 32.033 2007 32.099999999999994 2008 32.166 2009 32.18600000000001 2010 32.159000000000006 2011 32.131 2012 32.102999999999994 2013 32.075 2014 32.048 2015 32.019999999999996 2016 31.979 2017 31.924999999999997 2018 31.858000000000004 2019 31.778000000000006 2020 31.685000000000002 2021 31.578999999999994 2022 31.459999999999994 2023 31.328999999999994