Year	% of total
1960	0
1961	0
1962	0
1963	0
1964	0
1965	0
1966	0
1967	0
1968	0
1969	0
1970	0
1971	0
1972	0
1973	0
1974	0
1975	0
1976	0
1977	8.036739380022963
1978	9.134669204074779
1979	17.180134036643476
1980	17.233170540162465
1981	35.8478574396832
1982	40.743169398907106
1983	41.993506647391996
1984	41.66096230706383
1985	38.33574704320541
1986	38.6859091462672
1987	36.78888431144901
1988	36.29310664835369
1989	35.47206273110727
1990	35.33847030913805
1991	33.64777704963267
1992	33.36509311390212
1993	32.62659833985494
1994	29.60034130212857
1995	30.008589052861716
1996	28.07432286336183
1997	30.204117034809762
1998	31.144270098479343
1999	33.07657975438041
2000	32.12387104149994
2001	30.573530596353677
2002	29.744513374691483
2003	26.95609894931575
2004	26.461645989865456
2005	32.97016236434218
2006	27.828263193702014
2007	28.83008185119084
2008	29.64924062403141
2009	32.643716438413186
2010	28.26189354686764
2011	31.546509571298348
2012	32.64688756018236
2013	33.127973392087796
2014	34.628601638910915
2015	33.89798387684593