Year	% of total
1971	2.0857334410076858
1972	2.5873101902236204
1973	2.643642683783483
1974	3.026346819080408
1975	3.9923825463490026
1976	4.339000730033632
1977	5.000030246690718
1978	5.361139242942273
1979	5.724264590724491
1980	6.589380185110818
1981	8.828563037570229
1982	9.616939575080849
1983	10.965005296473713
1984	13.350620544374497
1985	15.357514750466136
1986	16.27585050043346
1987	16.254663948840147
1988	17.054310217163394
1989	17.599701065325075
1990	22.17232813706957
1991	22.749710916612212
1992	23.501247439263707
1993	24.78576758284707
1994	24.554148728784448
1995	24.860531188438053
1996	26.037112483819886
1997	26.21850959183082
1998	25.597539978690264
1999	25.76400036446693
2000	25.331569569095162
2001	25.700673712955496
2002	25.902051242343955
2003	25.599204676984584
2004	25.269904326286724
2005	24.72162808614357
2006	24.302611321087486
2007	23.05356719686369
2008	22.867993248983183
2009	23.017292319666076
2010	22.65247424754794
2011	22.642756363826965
2012	21.995941076247945
2013	21.81387322139364
2014	22.36541722248859
2015	16.076646584365925