Year	% of total
1971	11.553519893390048
1972	10.65004564244359
1973	10.33046354729409
1974	9.630688651978211
1975	10.041730274274537
1976	10.299380943469332
1977	8.867263668393585
1978	8.147859072325591
1979	7.96542842685032
1980	9.934256783227132
1981	12.292862898432602
1982	12.513515641215351
1983	11.56000591629147
1984	10.885768153571236
1985	9.420056575646544
1986	9.342535570082974
1987	8.44953836738917
1988	8.840515588201324
1989	8.930578970634478
1990	10.07221297605203
1991	9.802659081189907
1992	8.170289158171443
1993	7.594965968922562
1994	7.552064585797294
1995	7.2213674143985624
1996	7.7094289496054
1997	5.926897835431378
1998	6.3152906662475665
1999	6.639677296775889
2000	6.775633045207896
2001	6.936491410723581
2002	7.78535881651114
2003	8.06591157624759
2004	8.300061125489327
2005	8.537153881022506
2006	9.007829871539522
2007	9.389399714049718
2008	8.891238950730157
2009	7.6669474668442605
2010	8.257793264438519
2011	8.516307711675042
2012	8.414282584132085
2013	7.4005652116741425
2014	6.19820021673234
2015	7.101308356530381