Year	% of total
1971	11.39301464997212
1972	16.90416446050784
1973	16.13330768079694
1974	17.276099629040807
1975	17.42521546508814
1976	13.91377475714825
1977	15.611948277590296
1978	16.518558867014242
1979	17.462615311166896
1980	18.72536526094301
1981	18.159913313752888
1982	17.199152665331823
1983	14.286934244235697
1984	15.803647424895697
1985	17.70169038402629
1986	14.322054108481941
1987	15.131552303684003
1988	19.617110538753618
1989	18.03272204717143
1990	17.74401716711502
1991	25.681742161505554
1992	21.588707445336286
1993	23.01535799264547
1994	23.661491584445734
1995	28.16623359092903
1996	25.680521597392016
1997	30.63799258066774
1998	35.290489008524
1999	36.067836718595935
2000	28.455347171409866
2001	27.703931979356177
2002	29.31579428153832
2003	24.04606456293072
2004	29.227065965769306
2005	34.01107501725212
2006	29.277317893998116
2007	25.888152027629594
2008	26.471765502801897
2009	26.902893957499867
2010	32.79994721127039
2011	23.755221858417073
2012	20.52948582706639
2013	25.551797184638513
2014	28.842673537621543
2015	25.231334000788813