Year	% of total
1971	15.70966934312258
1972	13.210619533229211
1973	12.908348526355809
1974	10.268455953919018
1975	9.699148543773022
1976	8.800248120232435
1977	8.529125404135844
1978	9.668873670186494
1979	9.07361640117338
1980	7.762461183151233
1981	8.05577009767726
1982	9.274159004167352
1983	12.084638325885084
1984	11.999105586998066
1985	10.688433569202347
1986	11.463173678527381
1987	11.608433664108517
1988	11.823503029212274
1989	10.23975044597453
1990	10.574528431772247
1991	9.549611991636583
1992	11.057823568041304
1993	11.997418049651193
1994	13.783955503286712
1995	14.68644320123412
1996	14.293119149443767
1997	15.857248963213308
1998	16.353881751716077
1999	15.835095374397229
2000	15.290526360482403
2001	15.028354049758327
2002	15.09443502346
2003	14.984956143559296
2004	16.06220848373768
2005	16.925815185446393
2006	17.348369737704786
2007	19.105629471577164
2008	20.011299906086126
2009	17.395701016156593
2010	13.633951799237062
2011	13.70338506229054
2012	13.737797832278204
2013	11.673801066586204
2014	11.160050392721182
2015	11.722858004019956