Year	% of total
1960	0
1961	0
1962	0
1963	0
1964	0
1965	0
1966	0
1967	0
1968	0
1969	1.817687629531478
1970	5.078214860823556
1971	4.46104999839646
1972	12.045547225446217
1973	17.138821739957084
1974	19.0474907013099
1975	18.057656064589683
1976	21.999002438483707
1977	17.681412072346916
1978	19.869822485207102
1979	25.96502804354998
1980	29.778930980799167
1981	29.575182312767684
1982	28.82037022929839
1983	30.09866845483284
1984	37.211179497528
1985	40.61796640077786
1986	39.93739056613785
1987	39.12407517646058
1988	38.19162840577767
1989	42.486371839476085
1990	42.980797206866455
1991	40.35053793685395
1992	40.21127726711483
1993	38.36838646072954
1994	37.24090492204219
1995	39.99325279527053
1996	44.69609429165703
1997	40.98754678022971
1998	41.458012326656394
1999	37.61303569088288
2000	39.99455568326175
2001	37.73114920206029
2002	41.600855418926145
2003	42.02905198776759
2004	42.21091364597197
2005	40.390039626918615
2006	44.77114716106605
2007	42.031035987898676
2008	41.32108121009607
2009	41.52505511976362
2010	39.87615817840489
2011	42.47233176440656
2012	37.33636630466686
2013	37.82013969732247
2014	39.30986277139026
2015	34.931993887771