Year	% of total
1971	20.339077830567174
1972	19.50759300230159
1973	18.755887543025153
1974	14.850647582521875
1975	13.280437703565106
1976	12.176843668736094
1977	17.87671711267162
1978	21.177835217710342
1979	20.39476037975969
1980	25.723643589631745
1981	25.795649743745553
1982	28.512982197150123
1983	33.17879349621997
1984	36.949663982287824
1985	35.07969201785208
1986	36.93551724413306
1987	34.82654796324124
1988	30.49036741458833
1989	28.36720893654659
1990	30.131620435864264
1991	28.960025095014437
1992	33.37543336629939
1993	32.9480566528385
1994	32.718271393216085
1995	34.70938987246571
1996	34.07179359965892
1997	31.605654453863867
1998	30.202688033055242
1999	29.936945583750123
2000	30.574892275190273
2001	29.72206136327667
2002	28.722957744812934
2003	27.696795203346003
2004	29.76437787903094
2005	13.218434919630933
2006	10.642484624826231
2007	11.52867693510517
2008	11.838895821963046
2009	10.481624819193087
2010	15.626835979744808
2011	17.195970073503865
2012	18.73084166381655
2013	19.33335087171388
2014	18.06927786957438
2015	15.090619760213006