Annual % of total
1960 0
1961 0
1962 0.3516998827667057
1963 0.42238648363252373
1964 17.585848074921955
1965 46.82884448305821
1966 33.9622641509434
1967 8.553766532489938
1968 10.82272899080257
1969 9.494131089643709
1970 0
1971 0.006131207847946045
1972 0.7715164468539852
1973 0.9944495837187789
1974 1.0504825538233111
1975 1.2672709671741618
1976 1.0977503340194272
1977 0.9836472523039689
1978 1.00965060356085
1979 0.8919564640297318
1980 12.964045284325824
1981 24.322460664061683
1982 10.87632213768788
1983 5.225528814408342
1984 22.433119819140916
1985 22.6578595246692
1986 23.611533711585615
1987 26.97765642425874
1988 27.5775295544653
1989 27.793376529877612
1990 54.62483442514574
1991 59.79680081453298
1992 56.99071682969652
1993 58.105438630522286
1994 56.9600964395082
1995 34.15388399280575
1996 33.86911316160451
1997 38.40684734564742
1998 36.44400546851265
1999 35.16429881038673
2000 36.11921461897356
2001 32.71093805309735
2002 35.598380352927954
2003 35.23146956240337
2004 40.56371809251895
2005 41.220369938829016
2006 41.1483523679001
2007 32.67938221160763
2008 32.76834423398912
2009 29.950424142331656
2010 31.234160690298935
2011 30.597813519609346
2012 31.04063918158568
2013 30.702992510713283
2014 29.66744471973324
2015 35.759686887407774
2016 38.254067069008876