Year	% of total
1971	9.458695192232632
1972	10.407790392892137
1973	11.425430262377429
1974	10.876524034389808
1975	10.848781980370186
1976	11.956480315096146
1977	11.960598685347454
1978	12.36615678867743
1979	12.78226268661043
1980	12.754920802518136
1981	12.443634610514714
1982	11.744562911099909
1983	11.853409944913537
1984	10.934433670439146
1985	9.699026844310685
1986	9.459276380624766
1987	8.935705163300998
1988	8.400199199437203
1989	8.110080044076943
1990	13.485792535906885
1991	12.901039627641286
1992	12.049423483749914
1993	11.30280277157308
1994	10.550995675416813
1995	10.175208253240404
1996	9.578622824396643
1997	9.463877643646763
1998	9.711599113378472
1999	8.919006132340291
2000	8.497464364397786
2001	7.825444950333527
2002	7.422197132320366
2003	6.727174369255802
2004	6.516591839646615
2005	5.606884423425805
2006	4.973630961982859
2007	4.543584853156533
2008	4.438573726477983
2009	4.095718529779066
2010	3.7877029183126507
2011	3.999490521697618
2012	3.9473984277772516
2013	3.7027965865037413
2014	3.3821663475910313
2015	2.9728045662656015