Year	% of total
1971	81.50456794822992
1972	81.38835256611738
1973	77.27728183640006
1974	70.1569762343243
1975	64.87300392281175
1976	52.762460806573685
1977	47.02793672164255
1978	45.86561666454973
1979	47.253460207612456
1980	49.15171522893642
1981	45.79140971546035
1982	47.037741911564794
1983	45.064246858000374
1984	45.55873925501432
1985	36.44792467332821
1986	42.10186513629842
1987	44.1653440066248
1988	36.58070678127985
1989	38.262497744089515
1990	50.259841959137184
1991	51.39249180167392
1992	50.5925301881494
1993	45.78782535463326
1994	44.968924553536304
1995	42.02302041207016
1996	40.72712800824047
1997	44.99659792121255
1998	44.7580936769279
1999	43.36252926168495
2000	42.33380898489396
2001	45.38291909771673
2002	41.198510754345605
2003	45.97902097902098
2004	46.12320764737122
2005	42.356499590648596
2006	42.20913366445431
2007	52.316184176817195
2008	52.08146420240445
2009	49.79353955782072
2010	49.12532325010322
2011	55.04867760830018
2012	49.11226089010069
2013	45.025424319115835
2014	45.400302597651674
2015	46.20655697345205