Year	% of total
1971	17.635877444505297
1972	15.250291036088475
1973	14.245283018867925
1974	12.004684755026352
1975	13.482378654038794
1976	9.167999326656005
1977	9.569643506381675
1978	12.189857869801719
1979	17.057260207779656
1980	15.480421731728445
1981	11.523162513498367
1982	12.421297221666999
1983	10.13959964336749
1984	9.243069136086508
1985	8.491326931142392
1986	8.624168674202648
1987	9.43058787331013
1988	8.274016493419015
1989	9.076929612166008
1990	12.483058090247503
1991	16.120401337792643
1992	15.470706888246626
1993	15.38552254317366
1994	15.908272219994426
1995	16.10530187588671
1996	14.69582918492495
1997	15.112273348736963
1998	18.02867737405652
1999	18.809983812855727
2000	21.455694663911512
2001	26.02015066265398
2002	34.16673922308119
2003	40.143173437982874
2004	42.792624051384145
2005	40.133509857717094
2006	46.32508669443992
2007	49.79794324316173
2008	52.096986799844046
2009	54.65427220508378
2010	53.34818917241605
2011	54.330126077205364
2012	53.86618407176429
2013	55.74991759886455
2014	57.03624592034389
2015	59.86121913748883