Year	% of total
1971	0
1972	0
1973	0
1974	0.21773960465007897
1975	0.5052503895886825
1976	0.7005621957977936
1977	0.6387672576892964
1978	0.6784163182953686
1979	0.6237473905993137
1980	0.5543513485478615
1981	0.7421449615086143
1982	0.7359253641858998
1983	0.8666993292258223
1984	1.164806242670085
1985	1.3109947427055073
1986	1.1787032317746633
1987	1.0699453194248998
1988	1.2673117575645392
1989	1.199126524551993
1990	5.387706669944421
1991	5.3124870909239235
1992	5.191877422348958
1993	5.140102601246284
1994	4.888882816415164
1995	4.987695886881672
1996	5.218700632757929
1997	5.1483944806709765
1998	4.912619342629704
1999	5.215207937696835
2000	5.232881633930975
2001	5.446045818498134
2002	5.478201015831659
2003	5.603541212333667
2004	5.1389841170088655
2005	4.894481106674056
2006	4.700125722497036
2007	4.398532227963038
2008	4.410781381485613
2009	4.309355782471074
2010	4.000127330005558
2011	3.9727151874262603
2012	3.948967861938109
2013	3.8599358946990145
2014	4.0411926506081715
2015	0.12141836989679652