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 103.89833333333334 1991 94.29428571428572 1992 94.29428571428572 1993 7.037676767676768 1994 7.778484848484848 1995 8.4341 1996 8.499668874172185 1997 18.672453987730062 1998 11.388198757763975 1999 22.566153846153846 2000 15.604255319148935 2001 9.133919413919415 2002 19.381414392059554 2003 35.39081395348837 2004 8.952537931034483 2005 14.550148331273178 2006 26.381582969432316 2007 45.94678145695364 2008 7.391169265033408 2009 12.792743271221532 2010 13.134947478991595 2011 18.316117404737383 2012 7.583106893106893 2013 13.805176470588238 2014 16.453906056860323 2015 13.096428571428573 2016 13.030946428571427