Year	% of total
1971	0.22760790408739517
1972	0.20811707821696482
1973	0.22674475677903289
1974	0.2576370235569347
1975	0.24934080267280256
1976	0.2405445337676784
1977	0.2226813964119429
1978	0.23487426082006474
1979	0.29129040654391847
1980	0.41354567170244105
1981	0.48575709264772277
1982	1.281451437707559
1983	1.3707488810097377
1984	1.406076442835321
1985	1.402956112126317
1986	1.394725356034441
1987	1.3406435078800532
1988	1.3636371664868874
1989	1.3914644323850514
1990	1.0423173619319261
1991	1.0043525284451862
1992	0.9501770128117384
1993	0.890648727829098
1994	0.919627658392097
1995	1.038992525150574
1996	1.0028900565628767
1997	1.0380851635618569
1998	1.0437597469085922
1999	1.1009333383756295
2000	1.1210848128663555
2001	1.0854636468038046
2002	1.052780001452113
2003	1.031568152055241
2004	1.012397242686395
2005	1.095833279434949
2006	1.132836546173861
2007	1.179190086881575
2008	1.4499584330542188
2009	1.7293843152203288
2010	2.165908980037064
2011	2.500284381644245
2012	2.891737262152919
2013	3.631514574587015
2014	4.2020152496419145
2015	4.972734489951256