Year	% of total
1971	0.786133049756769
1972	1.4951777860791942
1973	1.5964422173856612
1974	1.580663393569949
1975	1.8301862810409364
1976	1.626614889086617
1977	1.4381523817008575
1978	1.269845183736614
1979	0.8332246674120388
1980	0.8366785471791754
1981	0.8422500633803481
1982	2.1283530078822404
1983	3.224562992794924
1984	3.987293051777475
1985	4.149216970729528
1986	4.430519968288685
1987	4.38508155165752
1988	4.078883526333661
1989	3.9397400265239817
1990	4.006184507945675
1991	4.123495567659196
1992	4.49901901198722
1993	4.730846796437089
1994	4.73603542993798
1995	5.53050296638295
1996	5.945083150926641
1997	6.1580592660770135
1998	6.217887241654315
1999	5.783867836267181
2000	6.207836588575112
2001	6.847210834374005
2002	6.726903679408245
2003	6.511453395605986
2004	6.282675052599155
2005	5.8204128088269735
2006	5.4312014910521365
2007	5.232372835941795
2008	4.608609563770771
2009	4.2586799679770735
2010	3.9014854999113133
2011	3.933882150175277
2012	4.016276430878241
2013	3.4034491819793273
2014	3.3385872379005295
2015	3.2035002531768053