Annual % of total
1960 11.926605504587156
1961 4.123711340206185
1962 3.7037037037037033
1963 8.730158730158731
1964 6.818181818181819
1965 7.236842105263158
1966 6.962025316455697
1967 5.217391304347826
1968 6.024096385542169
1969 6.0344827586206895
1970 5.660377358490567
1971 6.071428571428571
1972 4.273504273504273
1973 3.0716723549488054
1974 3.08641975308642
1975 3.0303030303030303
1976 5.535055350553506
1977 5.194805194805195
1978 3.237410071942446
1979 6.148867313915858
1980 4.081632653061225
1981 7.142857142857144
1982 7.2202166064981945
1983 11.235955056179776
1984 2.1097046413502114
1985 1.0416666666666665
1986 4.180064308681673
1987 2.5641025641025643
1988 3.977272727272727
1989 3.543307086614173
1990 3.7082022471910117
1991 3.474
1992 3.4378125
1993 3.6670000000000003
1994 2.727520661157025
1995 1.8736496350364964
1996 1.959465648854962
1997 2.324154929577465
1998 2.0247239263803682
1999 1.3174850299401197
2000 1.5556969696969698
2001 1.537065868263473
2002 2.291875
2003 1.6560645161290324
2004 1.5556969696969698
2005 2.5733333333333333
2006 2.4595731707317077
2007 1.4923837209302326
2008 1.8541011235955058
2009 2.1698224852071006
2010 5.686791443850268
2011 18.586164383561645
2012 25.428102189781022
2013 38.54730375426621
2014 33.423803278688524
2015 31.6996686746988
2016 32.68413043478261