Annual % of total
1960 38.243626062322946
1961 36.315789473684205
1962 27.881040892193305
1963 35.92677345537758
1964 31.00358422939068
1965 31.46067415730337
1966 31.33208255159475
1967 32.02725724020443
1968 29.985228951255532
1969 28.688524590163933
1970 28.82882882882883
1971 29.468599033816428
1972 29.385474860335197
1973 30.769230769230766
1974 30.98729227761486
1975 29.39585211902615
1976 29.392173189009156
1977 28.023598820058996
1978 28.85225110970196
1979 27.706635622817227
1980 27.292110874200425
1981 30.132450331125828
1982 30.748373101952275
1983 31.34171907756813
1984 13.871517907902216
1985 26.198212835093422
1986 24.86732373009856
1987 24.69691721510218
1988 23.181530676786842
1989 23.247744621790424
1990 18.942868157286043
1991 12.620840108401085
1992 13.601547433903576
1993 13.863426160337552
1994 10.624350775193799
1995 9.9165953307393
1996 13.250149597238206
1997 13.21325117370892
1998 14.196222222222223
1999 13.926933797909408
2000 14.627255555555555
2001 16.59756967670011
2002 14.897187500000001
2003 16.818571428571428
2004 18.06649581589958
2005 15.251537070524412
2006 15.707278582930757
2007 18.419493087557605
2008 19.706237471087125
2009 17.07144428152493
2010 17.27154437456324
2011 19.5122631913541
2012 20.303284714119023
2013 19.99093579978237
2014 18.719508830022075
2015 19.458416184971096
2016 16.791106219042376