Year % of total population 1960 40.639 1961 40.144 1962 39.645 1963 39.147 1964 38.65 1965 38.157 1966 37.666 1967 37.178 1968 36.691 1969 36.208 1970 35.727999999999994 1971 35.25 1972 34.961 1973 34.759 1974 34.55800000000001 1975 34.357 1976 34.156000000000006 1977 33.956 1978 33.757000000000005 1979 33.55800000000001 1980 33.36 1981 33.163 1982 33.114000000000004 1983 33.134 1984 33.153999999999996 1985 33.17400000000001 1986 33.194 1987 33.214 1988 33.233999999999995 1989 33.254000000000005 1990 33.274 1991 33.294 1992 33.257999999999996 1993 33.19799999999999 1994 33.138000000000005 1995 33.078 1996 33.018 1997 32.958 1998 32.897999999999996 1999 32.837999999999994 2000 32.778000000000006 2001 32.718 2002 32.617999999999995 2003 32.498999999999995 2004 32.379999999999995 2005 32.262 2006 32.144000000000005 2007 32.025999999999996 2008 31.908 2009 31.790999999999997 2010 31.673000000000002 2011 31.555999999999997 2012 31.316000000000003 2013 31.021 2014 30.727999999999994 2015 30.435000000000002 2016 30.144999999999996 2017 29.855999999999995 2018 29.561999999999998 2019 29.263999999999996 2020 28.961 2021 28.653999999999996 2022 28.343000000000004 2023 28.027