Annual % of total
1960 65.48672566371681
1961 59.70149253731344
1962 52.65957446808511
1963 55.440414507772026
1964 56.76855895196506
1965 53.81818181818182
1966 52.68456375838926
1967 43.42857142857143
1968 40.7185628742515
1969 56.03112840466926
1970 40.131578947368425
1971 39.458413926499034
1972 40.909090909090914
1973 42.95302013422819
1974 40.15296367112811
1975 41.206896551724135
1976 44.464944649446494
1977 40.79754601226994
1978 43.293718166383705
1979 52.04582651391162
1980 52.49999999999999
1981 51.20147874306839
1982 47.29493891797557
1983 48.401162790697676
1984 40.0259067357513
1985 44.09613375130617
1986 36.28938156359393
1987 64.55399061032864
1988 63.55498721227622
1989 67.23910171730515
1990 62.56199324324324
1991 62.767262773722635
1992 64.8776923076923
1993 65.79029411764706
1994 66.006
1995 66.00600000000001
1996 66.19245762711866
1997 66.006
1998 65.6567619047619
1999 60.37134146341464
2000 64.76779220779221
2001 60.663950617283945
2002 40.00363636363636
2003 45.90540740740741
2004 49.65053097345133
2005 52.545426829268294
2006 58.59639175257732
2007 50.80970338983051
2008 64.06808656036446
2009 82.44638333333334
2010 67.7147289504037
2011 62.06382544861337
2012 64.70763636363637
2013 56.233078730904815
2014 48.3142509603073
2015 59.34206508135168
2016 47.04081190798376