Year	% of total
1971	0.7742843735335524
1972	0.6380120886501007
1973	0.5817932922655715
1974	0.494783263418307
1975	0.5840586349060926
1976	0.7868923143257519
1977	0.8183306055646482
1978	0.8783783783783784
1979	0.8442608227052272
1980	0.8935409752361502
1981	0.9183503088996493
1982	1.1540729508887204
1983	1.6476552598225602
1984	1.4892198266281396
1985	1.3888888888888888
1986	1.8990775908844275
1987	1.7330690030056914
1988	1.9331953887082471
1989	1.8022570321711302
1990	5.241672109732201
1991	5.175091428285157
1992	7.794124223046997
1993	7.2907553222513855
1994	7.0657119120148755
1995	6.704249473721768
1996	5.655158949663228
1997	5.234705829353996
1998	3.2695936241516232
1999	2.6308934618390207
2000	2.3479215529717052
2001	4.878794291222873
2002	4.467495592040485
2003	3.873668026223067
2004	3.9798468989220432
2005	3.423900617330996
2006	2.59942154736081
2007	4.623220359260968
2008	5.2274554468712315
2009	7.168736207634795
2010	4.267465334083463
2011	7.6255839788169775
2012	7.54541153531849
2013	8.653938274139465
2014	10.130508900874718
2015	11.926459469139242