Year	% of total
1971	13.27151114364978
1972	14.532877727398057
1973	14.836150611119994
1974	14.052712106166936
1975	12.271841582939508
1976	13.039382799161093
1977	11.27157680719113
1978	11.81677171708539
1979	11.336825318645529
1980	10.58231337096569
1981	9.188976263913553
1982	7.867171116451252
1983	6.596474108680956
1984	6.824501200759283
1985	5.283098173007874
1986	4.919511201606037
1987	4.736280362662294
1988	4.2566270632113525
1989	4.825467703779797
1990	10.010416008481826
1991	9.83394455209108
1992	9.202391544749009
1993	8.0617151921597
1994	7.7661379306382905
1995	7.9050055001377375
1996	7.18936182289039
1997	6.682146366578589
1998	6.83152883095704
1999	6.091325885088956
2000	5.215944911722305
2001	4.767838647439173
2002	4.951028273197476
2003	4.5332491317329495
2004	3.7973589355076394
2005	3.5585636817804063
2006	3.409643342348238
2007	2.783168133545012
2008	2.590133772537215
2009	2.5229016647907754
2010	1.8842629030301261
2011	1.9412268619136155
2012	1.9612016721000978
2013	1.3448196459995343
2014	1.353575985258412
2015	1.448981334176425