Year	% of total
1971	15.869492117856016
1972	12.904151843002099
1973	12.793641014491813
1974	9.783499954163478
1975	9.528317837920355
1976	9.731756206134392
1977	10.869158628347716
1978	11.702095058232434
1979	10.324519441163277
1980	7.696140501730514
1981	7.240113167353241
1982	7.163697127552142
1983	10.206991519813933
1984	11.109176170006345
1985	8.001134718950585
1986	8.058772040846426
1987	9.359525467596898
1988	8.739999845259975
1989	7.041725181484983
1990	7.220072040985513
1991	6.7319148625984715
1992	8.373964436066716
1993	8.638619623678172
1994	10.083832954608832
1995	11.005959825058067
1996	9.746185341596577
1997	10.61172285402963
1998	10.500569582288078
1999	9.47918573941325
2000	9.436523508218038
2001	10.02849839565257
2002	10.402411364362576
2003	11.56033191728972
2004	12.997419575319338
2005	12.571811805058589
2006	12.75061376081135
2007	13.481915087085863
2008	13.723933777319298
2009	12.391201870945652
2010	9.733475832529177
2011	10.508925756098767
2012	11.063603659714522
2013	10.27883311500278
2014	10.520822233561562
2015	11.545038211573607