Year	% of total
1971	38.35800807537012
1972	40.71246819338422
1973	42.8226779252111
1974	44.72477064220183
1975	46.44808743169399
1976	47.24576271186441
1977	47.99588900308325
1978	48.70259481037924
1979	49.369544131910764
1980	50
1981	50.59687786960514
1982	51.162790697674424
1983	51.70008718395815
1984	52.21088435374149
1985	50.99601593625498
1986	48.616600790513836
1987	47.89272030651341
1988	46.236559139784944
1989	48.63013698630137
1990	43.682310469314075
1991	42.96577946768061
1992	42.51012145748988
1993	39.81900452488688
1994	40.25974025974026
1995	38.26086956521739
1996	41.31455399061033
1997	44.559585492227974
1998	40
1999	44.623655913978496
2000	47.42268041237113
2001	47.524752475247524
2002	46.29854368932039
2003	44.18516049147538
2004	43.11200109224958
2005	42.68505586592179
2006	43.74860708714063
2007	38.298564326534404
2008	39.37513466925232
2009	40.83400388128934
2010	38.14623338257016
2011	31.34297305731821
2012	29.819089207735495
2013	24.176303731180447
2014	27.410799039589033
2015	27.20390187085972