Year	% of total
1971	16.170212765957448
1972	13.461538461538462
1973	10.582010582010582
1974	8.061420345489443
1975	5.733558178752108
1976	6.291390728476822
1977	6.304728546409807
1978	3.5211267605633805
1979	5.499276410998553
1980	5.345501955671447
1981	5.815423514538559
1982	3.8461538461538463
1983	3.9145907473309607
1984	3.3976124885215793
1985	0.904866715578381
1986	0.23505708529214236
1987	0.16130766749112807
1988	0.14008405043025815
1989	0.09041219742736202
1990	0.06989148427441604
1991	0.0545126230792818
1992	0.05158247669577392
1993	0.08906985621580354
1994	0.043935524617623636
1995	0.06155740227762388
1996	0.07138395645578656
1997	0.07077697389116074
1998	0.07075054536878722
1999	0.0692707331152588
2000	0
2001	0
2002	0
2003	0
2004	0
2005	0
2006	0
2007	0
2008	0
2009	0
2010	0
2011	0
2012	0
2013	0
2014	0
2015	0