Year	% of total
1971	100
1972	100
1973	100
1974	100
1975	100
1976	100
1977	100
1978	100
1979	100
1980	100
1981	100
1982	77.96797349530647
1983	46.33509443128682
1984	30.617256390222124
1985	22.090483619344774
1986	15.14528636830795
1987	4.897666975490609
1988	1.764636680914474
1989	2.94214392748803
1990	1.793489529338586
1991	3.555821045681768
1992	4.2054602228779325
1993	5.015299026425591
1994	2.000523501477022
1995	2.4000573148015474
1996	2.1025244356936925
1997	1.264467092762135
1998	1.1490594264251839
1999	0.9763373788053427
2000	0.48833423765599565
2001	0.477923038973853
2002	0.5041673952322667
2003	0.56605367653271
2004	0.6382634924054724
2005	0.3927076018829159
2006	0.3780718336483932
2007	0.2875333744095297
2008	0.36058324998684005
2009	0.35113084787772386
2010	0.2787401985047021
2011	0.2940574818451468
2012	2.134177736587375
2013	0.40349353899586293
2014	0.5788168082387432
2015	0.4917170654746253