Year Total 1965 35326000 1966 35222000 1967 34062000 1968 35259000 1969 36647000 1970 37100000 1971 38653000 1972 38102000 1973 37283000 1974 37145000 1975 37938000 1976 38678000 1977 39514000 1978 39668000 1979 39680000 1980 38451000 1981 38295000 1982 38592000 1983 38375000 1984 39098000 1985 38249000 1986 38076000 1987 37633000 1988 38074000 1989 36608000 1990 31455000 1991 28878000 1992 25823000 1993 24610000 1994 22841000 1995 22660000 1996 22564000 1997 23173000 1998 21254000 1999 18408000 2000 21643000 2001 21185000 2002 20792000 2003 21044000 2004 20983000 2005 20247000 2006 21035000 2007 21389000 2008 19741000 2009 17655000 2010 18768000 2011 18414000 2012 17407000 2013 17203000 2014 16037000 2015 16580000 2016 16900000