Annual % of total
1960 48.118475358096624
1961 41.75257731958763
1962 38.80890052356021
1963 35.783292290206475
1964 35.09306803594352
1965 28.550745620385115
1966 23.018633540372672
1967 23.06509482316761
1968 23.64336818932306
1969 24.920251329144516
1970 21.387073347857662
1971 19.183157133821272
1972 19.97010711616707
1973 19.832194832194833
1974 20.879811468970935
1975 19.527521476296535
1976 23.855835240274597
1977 23.43921139101862
1978 29.660238751147844
1979 30.330026321117636
1980 34.38680433140267
1981 34.028618210294006
1982 27.951315005532386
1983 30.878461809843
1984 35.60704677601319
1985 38.34908446544596
1986 31.898507873203602
1987 35.28588691725498
1988 37.84695383318108
1989 36.17154811715481
1990 37.1068676686217
1991 38.51913114456739
1992 36.15095256312165
1993 39.47546763935652
1994 43.443517437009845
1995 41.77594936708861
1996 45.09759469394278
1997 43.38456614978555
1998 37.18224026540947
1999 36.546706777561496
2000 35.864724137931034
2001 38.80092977574071
2002 40.90115384615384
2003 43.81888578998745
2004 43.02006501182033
2005 34.70624413992066
2006 42.442433601909876
2007 42.94501996927803
2008 37.39485704200494
2009 37.34004983388704
2010 43.32607708300016
2011 42.078691944847606
2012 36.44735276259866
2013 40.02356246264196
2014 37.29758448873483
2015 37.12387902849136
2016 38.61140013126231