Year	% of total
1971	0.5679079296215955
1972	0.6721878722559419
1973	0.4917852629265344
1974	0.6064320926471739
1975	0.5970253473919419
1976	0.5082884484651989
1977	0.5135047711466926
1978	0.5121266877934059
1979	0.5238386470603877
1980	0.5182336868506507
1981	0.5992594271896018
1982	1.4037121329921827
1983	1.5077824212708546
1984	1.251447222206061
1985	1.159678858162355
1986	1.8051585764643014
1987	1.9086377689444127
1988	1.4751146037982972
1989	2.676423194931903
1990	3.4017463072024925
1991	4.18316335479991
1992	4.821742624880999
1993	4.954481841233771
1994	5.599097266467594
1995	6.947552282490676
1996	7.228388081195221
1997	8.500289837902335
1998	9.960277994485372
1999	10.812063689832714
2000	9.82362275491146
2001	9.509819423262963
2002	10.30053955597197
2003	11.185903690171271
2004	11.195615146982927
2005	10.54515018388723
2006	10.256609079536409
2007	11.571792321898872
2008	10.243706938722587
2009	12.65799049822196
2010	11.566995025607095
2011	10.62719164364898
2012	7.61347011572959
2013	5.241437102418906
2014	4.63653355306791
2015	4.923196172968408