Year	% of total
1960	100
1961	100
1962	100
1963	92.0245398773006
1964	93.80733944954129
1965	92.23880597014926
1966	82.48587570621469
1967	88.6861313868613
1968	53.156146179402
1969	53.31412103746397
1970	73.97454031117398
1971	66.58624849215921
1972	41.03585657370518
1973	43.625498007968126
1974	29.850746268656714
1975	30.592734225621417
1976	36.36363636363637
1977	39.175257731958766
1978	35.78847969782814
1979	32.687105500450855
1980	29.009762900976295
1981	33.72043010752688
1982	36.824450242266124
1983	20.23172905525847
1984	26.00557546794106
1985	19.10071942446043
1986	14.785214785214784
1987	21.33461661854347
1988	20.3798613204703
1989	14.058106841611998
1990	17.61798882681564
1991	17.96298550724638
1992	6.873757131214344
1993	15.375026778882939
1994	18.04701570680628
1995	12.295553914327916
1996	14.569661256175017
1997	18.919889042995838
1998	19.36346228239845
1999	13.599941747572814
2000	16.48764483627204
2001	12.797583892617448
2002	18.95255516840883
2003	20.86678173719376
2004	23.703586168432793
2005	25.97015458937198
2006	16.607435555555554
2007	25.0522555410691
2008	26.48471134436819
2009	14.857800242620298
2010	15.850812163202463
2011	14.961021897810218
2012	9.274459917199849
2013	15.848682197496524
2014	7.753848444738584
2015	13.014254901960784
2016	12.591652317880794