Year	% of total
1970	5.716402446574053
1971	5.2649957225286235
1972	4.9681830190548535
1973	4.866527558654385
1974	5.273087340364978
1975	7.182573348553413
1976	7.3604418773197455
1977	7.711917689535137
1978	8.953508561481422
1979	10.289856239930598
1980	10.322821893205418
1981	6.2325470863235495
1982	8.685604103982065
1983	17.11600474041838
1984	21.381671115649507
1985	20.514104938188893
1986	20.09911568627451
1987	20.093624640076914
1988	13.135163549889297
1989	13.668694084242377
1990	0
1991	0
1992	0
1993	0
1994	0
1995	0
1996	0
1997	0
1998	0
1999	0
2000	0
2001	0
2002	0
2003	0
2004	0
2005	0
2006	0
2007	0
2008	0