Annual % of total
1960 24.068479355488417
1961 22.9126213592233
1962 25.71428571428571
1963 21.38888888888889
1964 22.47097844112769
1965 18.158347676419965
1966 21.797451374916164
1967 21.86865267433988
1968 18.892508143322477
1969 18.18753933291378
1970 16.59125188536953
1971 15.511846222619582
1972 19.726651480637813
1973 16.24191707873716
1974 13.961145867632533
1975 15.907590759075907
1976 16.576691013020007
1977 14.232101616628176
1978 13.965227145260794
1979 11.121323529411766
1980 10.694572217111316
1981 11.378353376503238
1982 11.82287188306105
1983 14.032557181125076
1984 12.062577192260191
1985 13.752052545155994
1986 21.305107787919983
1987 22.493620123951878
1988 20.935064935064936
1989 20.864
1990 19.440331339162448
1991 20.797910447761193
1992 16.57844022169438
1993 18.34911470361817
1994 18.889025950942056
1995 21.637811643835615
1996 27.886462443752162
1997 25.353442136498515
1998 27.623552334943636
1999 25.46652760736196
2000 30.14893060979273
2001 34.623949079089925
2002 34.27452051215051
2003 32.04426328186338
2004 32.48734171211762
2005 31.683407507305013
2006 31.85105867070795
2007 31.614718206578672
2008 28.163846153846155
2009 26.07676691729323
2010 24.663069325382033
2011 19.854720539885793
2012 19.06961928512053
2013 18.789383791024783
2014 25.038247220405495
2015 26.693901821060965
2016 25.758524096385543