Annual % of total
1960 83.60197368421053
1961 82.57800367076096
1962 80.51777618706751
1963 77.89855072463769
1964 74.99358371118144
1965 73.27210830496398
1966 71.30611324159712
1967 68.3927147035363
1968 66.06911846239142
1969 62.02419755814596
1970 54.137724550898206
1971 50.025662959794694
1972 49.620393460792464
1973 48.76658319569503
1974 46.53939175629084
1975 47.11905239911665
1976 43.41240784392397
1977 41.66626442052421
1978 41.66478987432999
1979 44.220523511697934
1980 47.238654110075245
1981 46.25741670470105
1982 43.42731600146466
1983 43.225256665178755
1984 44.84784889821616
1985 45.93742321238431
1986 44.835737179487175
1987 45.62407459282084
1988 43.463283481767775
1989 44.51255601589584
1990 48.848467917346376
1991 50.85999488141956
1992 54.88859785960457
1993 57.965870307167236
1994 55.066664798206276
1995 54.471947339550184
1996 54.49883944787505
1997 57.31018737118231
1998 56.849735125518876
1999 57.347575620767486
2000 58.08974844218786
2001 61.9054395842356
2002 59.86715791886317
2003 59.48825015660889
2004 59.85495337007206
2005 55.89341269841269
2006 55.15102103328569
2007 57.785564424173316
2008 59.201197281631025
2009 57.740102397021175
2010 59.55502341137123
2011 64.51025971411315
2012 60.78345079787234
2013 58.255755901557
2014 59.22079090693819
2015 57.97125755202506
2016 53.52027791087686