Year	% of total
1971	0.35384661600988127
1972	0.3363917592633673
1973	0.30933335845904913
1974	0.30679971994168626
1975	0.27571415654213816
1976	0.2681550476167165
1977	0.2648511148365347
1978	0.26069331125441364
1979	0.2328837265715583
1980	0.24509270120834453
1981	0.23836570618473
1982	0.2302496619622925
1983	0.2220770697702638
1984	0.21584711062700734
1985	0.20555831331562757
1986	0.609030182002032
1987	0.5456384973850474
1988	0.45569317666161135
1989	0.43634509504643354
1990	0.4125040105289508
1991	0.3891086295695972
1992	0.36236514983555895
1993	0.369144053855107
1994	0.2817782069968773
1995	0.36504291756419677
1996	0.36600247915013184
1997	0.3370026312130846
1998	0.3499293463059421
1999	0.34248586316263363
2000	0.37190573827872786
2001	0.382338916290788
2002	0.2997555981866737
2003	0.5211031026115981
2004	0.6218258412876693
2005	0.5882133963788381
2006	0.9463569637024555
2007	0.6643344482698066
2008	0.7724120569610303
2009	0.886316176609741
2010	0.9070753170208605
2011	0.9355383984282509
2012	0.9784967591749828
2013	1.285532514786698
2014	2.303511017107424
2015	2.4196369720517614