Year	% of total
1971	0
1972	0
1973	0
1974	0
1975	0
1976	0
1977	0
1978	0.0009208115981519265
1979	0.17905846214517288
1980	0.5460238801274834
1981	0.7920975504560411
1982	0.9481793695464303
1983	1.143569112587852
1984	1.1577780877223216
1985	1.1752374905886287
1986	1.0195351242984454
1987	0.8940104565524323
1988	0.9035161222449514
1989	0.9040267995338447
1990	0.8945445983610026
1991	0.7984314289264506
1992	0.7265906038052772
1993	0.6568213657261479
1994	0.7513859232804745
1995	0.9192202704720995
1996	0.8279470600689837
1997	0.9039589664995136
1998	0.9884996726467764
1999	1.0913694916795855
2000	1.1734082725911081
2001	1.0869406264315136
2002	0.9993347946252285
2003	0.8900071257245522
2004	0.8294576549940628
2005	0.8533724271737111
2006	0.8806591183007443
2007	0.9085202083411663
2008	1.2761122786968722
2009	1.6651192868984293
2010	1.9372027381239023
2011	2.3307313492945805
2012	2.7715973898602666
2013	3.5861783101763933
2014	4.032186355492063
2015	4.75944216909399