Year	% of total
1971	1.1981852727907247
1972	1.2439638883056896
1973	1.1587306491981584
1974	1.0948548794264914
1975	1.0971052131500603
1976	0.9596481290193595
1977	1.1058092107868371
1978	1.1815947981442219
1979	1.4001293640651868
1980	1.295020806428469
1981	1.3172793574658723
1982	1.4320562302336133
1983	1.8369909042795427
1984	1.5898322091532417
1985	1.5830071973647524
1986	1.579692076308082
1987	1.753298808346981
1988	1.5534061885022818
1989	1.5361836017027577
1990	1.7318834400707295
1991	1.706225440209577
1992	2.0266245263349494
1993	1.9660602597072738
1994	2.071980956849112
1995	2.029745900776848
1996	2.3187470389112805
1997	2.39721801923489
1998	2.3341248430448673
1999	2.500029876074045
2000	2.248717434295377
2001	2.7442254069916108
2002	2.9739260742150773
2003	3.2812847375658385
2004	3.2357473035439135
2005	3.395255475358097
2006	3.5675363728934006
2007	4.194120144581452
2008	4.4602616899930245
2009	5.114551800927227
2010	6.528807841084257
2011	6.57048238199027
2012	7.290128550334404
2013	8.225762393713142
2014	9.857089888953038
2015	12.11841444712646