Year % of total 1960 100 1961 100 1962 100 1963 100 1964 100 1965 100 1966 100 1967 100 1968 100 1969 100 1970 100 1971 100 1972 100 1973 100 1974 100 1975 100 1976 100 1977 100 1978 100 1979 100 1980 100 1981 100 1982 100 1983 100 1984 100 1985 100 1986 100 1987 100 1988 100 1989 100 1990 97.78666666666666 1991 97.78666666666666 1992 73.33999999999999 1993 77.92375 1994 82.5075 1995 80.674 1996 91.67500000000001 1997 80.674 1998 70.00636363636364 1999 73.34 2000 78.98153846153846 2001 73.34 2002 85.56333333333333 2003 83.81714285714285 2004 89.383125 2005 89.383125 2006 84.12529411764706 2007 101.86111111111111 2008 91.675 2009 32.269600000000004 2010 95.74944444444444 2011 90.5964705882353 2012 66.006 2013 99.22470588235294 2014 97.78666666666666 2015 97.78666666666666 2016 99.82388888888889