Year	% of total
1971	9.45340223267973
1972	10.320352189868496
1973	11.246278593208823
1974	10.649426604974057
1975	10.63279408298877
1976	11.615528432314091
1977	11.621546675761204
1978	12.027414976575026
1979	12.364294666548124
1980	12.351990483397639
1981	12.071562352799337
1982	11.490331652604464
1983	11.684034781542794
1984	10.811746166504042
1985	9.627385717371338
1986	9.433037518716803
1987	8.933766696739474
1988	8.44188213897825
1989	8.13640510553683
1990	13.269605158480072
1991	12.770158425336431
1992	12.052111330952352
1993	11.390468318997847
1994	10.7292259149204
1995	10.537534030420256
1996	10.038416239833234
1997	9.941931192503647
1998	10.171488581380547
1999	9.468921861759373
2000	9.057643118657518
2001	8.37131823102851
2002	7.920330810730482
2003	7.039972044443464
2004	6.872306175179366
2005	6.0908781595465715
2006	5.592802249333932
2007	5.226107937223773
2008	5.151262243898915
2009	4.797032639992082
2010	4.32472814739023
2011	4.5019048358996905
2012	4.435750976096668
2013	4.173639558806773
2014	3.8305840356243044
2015	3.451876939958335