Year	% 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