Year	% of total
1960	0
1961	0.1721170395869191
1962	0.17301038062283738
1963	0.1529051987767584
1964	0.09017132551848511
1965	0.12254901960784313
1966	0.10416666666666667
1967	0.0947867298578199
1968	0.09442870632672332
1969	0.08583690987124462
1970	0.07342143906020558
1971	0.06373486297004462
1972	0.05830903790087463
1973	0.04418912947414935
1974	0.048239266763145196
1975	0.044782803403493054
1976	0.050352467270896276
1977	0
1978	0
1979	0.0429553264604811
1980	0.04338394793926247
1981	0.04945598417408506
1982	0
1983	0
1984	0
1985	0
1986	0
1987	0
1988	0
1989	0
1990	1.8654082998661312
1991	1.8335000000000001
1992	2.1597055214723926
1993	1.7629807692307695
1994	1.6628400954653937
1995	1.6898617511520737
1996	1.8659513274336281
1997	1.9530760869565216
1998	1.9240432098765432
1999	1.9106613226452906
2000	1.8954671968190853
2001	1.3824007936507936
2002	2.289639024390244
2003	2.1468744098205854
2004	1.6652412488174075
2005	1.4584659090909093
2006	0.6081260364842455
2007	0.7931946755407654
2008	1.3341476091476092
2009	1.7218147208121828
2010	1.5197459893048129
2011	2.7984999999999998
2012	2.7334880450070322
2013	3.0961477572559364
2014	3.716554054054054
2015	3.571426611796982
2016	2.507754838709677