Annual % of total
1960 0.06850419084461637
1961 0.07508397549891327
1962 0.0784841349927122
1963 0.06586473463445072
1964 0.07074887686157984
1965 0.09042220212839952
1966 0.19170442662948764
1967 0.8632455302306536
1968 2.0197333828214403
1969 4.010560351220669
1970 6.243979332691129
1971 8.907395673033403
1972 10.401076263348187
1973 11.805867286314067
1974 14.17491525423729
1975 15.28966573565186
1976 15.329723021379815
1977 15.555104878896742
1978 14.367847117253291
1979 15.211024528005856
1980 15.082527034718268
1981 15.176961059696637
1982 13.217082072558256
1983 16.04546274580552
1984 15.96229434067272
1985 16.065286065286067
1986 13.11755899336993
1987 14.651493598862023
1988 14.860963934665838
1989 15.420576693397031
1990 17.11557405543866
1991 17.553075640575642
1992 18.450889343897444
1993 19.56554808827536
1994 19.27967536988686
1995 21.210796019900496
1996 22.65588949351193
1997 22.120209190672153
1998 23.925631856628424
1999 26.44138429573197
2000 26.107989427012278
2001 25.508487409160047
2002 27.642266125394677
2003 28.558151515151515
2004 29.266532187335553
2005 30.523523189585035
2006 31.745791072250345
2007 32.799297255951814
2008 31.783181520620968
2009 34.62071837062305
2010 36.022497417112795
2011 34.51361829025845
2012 34.67740101095199
2013 34.339456577994
2014 32.21640084294587
2015 33.603894957983194
2016 34.72219783715013