Year % of total 1970 74.12146085788855 1971 75.2180469742263 1972 76.47768993510147 1973 74.40614032261998 1974 72.37730205582392 1975 70.1421938497656 1976 55.1421080279916 1977 62.93611914546889 1978 62.39112970985457 1979 62.22164309670756 1980 62.053517933036076 1981 67.6948143539786 1982 67.21671907171151 1983 66.732511440752 1984 66.21250761250747 1985 66.3834953605774 1986 66.9078389203738 1987 67.1661793921981 1988 67.17832129457888 1989 67.13339647624093 1994 0 1995 80 1996 80 1997 80 1998 80 1999 80 2000 80 2001 80 2002 80 2003 80 2004 80 2005 80 2006 80 2007 80 2008 80