Year	% of total
1960	0
1961	0
1962	0
1963	0.07471259750797336
1964	0.10981818181818183
1965	0.08695474956352792
1966	0.10664550290795005
1967	0.09047740134710797
1968	0.508578804784408
1969	0.2706934665138366
1970	0.4949597159112604
1971	1.9235190436048737
1972	2.929788280034291
1973	5.647935249054913
1974	5.183499991182124
1975	4.536595928973582
1976	5.839983904500034
1977	8.180084837870234
1978	9.099260149253297
1979	9.821781626799588
1980	10.188652961063873
1981	10.261486451877273
1982	9.89727609984794
1983	11.91918201211289
1984	11.947095032150294
1985	13.188046405815545
1986	15.212453946610086
1987	15.569030001128468
1988	16.38212233956326
1989	15.991350831881796
1990	15.137094147593256
1991	16.703345979337648
1992	15.488228431283984
1993	17.65344839574755
1994	19.40601756788615
1995	17.4719868572602
1996	16.191709618469304
1997	14.387726638772664
1998	12.732329266143088
1999	12.69395192980335
2000	12.021050337188488
2001	13.004001492081793
2002	12.56341926748043
2003	12.703420621431553
2004	15.067890275311946
2005	14.832625329560178
2006	16.031078993532848
2007	14.871200153990305
2008	15.196259966511889
2009	14.77761648172297
2010	15.013181950663734
2011	14.707805167823837
2012	14.900157228999875
2013	15.549008260114693
2014	16.119074992215758
2015	15.546560515251812