Annual % of total
1964 50
1965 51.57894736842105
1966 48.71794871794872
1967 39
1968 33.0188679245283
1969 22.115384615384613
1970 25.806451612903224
1971 24.08759124087591
1972 25.503355704697984
1973 26.282051282051285
1974 25.333333333333336
1975 32.278481012658226
1976 28.30188679245283
1977 23.5632183908046
1978 21.85792349726776
1979 14.367816091954023
1980 24.226804123711336
1981 21.21212121212121
1982 27.160493827160497
1983 20.38216560509554
1984 19.736842105263158
1985 15.789473684210526
1986 13.245033112582782
1987 13.422818791946309
1988 8.108108108108107
1989 5.194805194805195
1990 24.955972222222222
1991 20.887974683544304
1992 21.352151898734174
1993 20.418522727272727
1994 19.745384615384616
1995 19.342417582417582
1996 20.55131868131868
1997 20.072000000000003
1998 20.327934782608693
1999 14.897187500000001
2000 19.168409090909087
2001 13.751249999999999
2002 20.893372093023256
2003 19.168409090909087
2004 17.73054945054945
2005 17.32758241758242
2006 16.95494623655914
2007 16.089897959183673
2008 13.667909090909092
2009 12.441607142857142
2010 16.219423076923075
2011 21.551666666666666
2012 19.317232142857144
2013 18.18347107438017
2014 18.335
2015 18.946166666666667
2016 15.908308823529413