Year	% of total
1971	6.471988921135874
1972	6.547026237898507
1973	6.931548795600929
1974	8.288336594639386
1975	7.351088971217323
1976	9.357473036632188
1977	10.889082554345126
1978	12.317963350976298
1979	11.506879846970419
1980	7.713655158692695
1981	9.077834444663706
1982	7.358147078788889
1983	7.414394177882571
1984	7.281409488932082
1985	6.1112320169310115
1986	6.501438341982089
1987	5.915139700654473
1988	3.7016386849722713
1989	3.911010640697871
1990	6.493364808998884
1991	5.954102740285512
1992	4.858883118548438
1993	5.446256581481956
1994	5.105671825988583
1995	4.825778713567395
1996	4.838904450816547
1997	5.230081363217684
1998	5.182534069613214
1999	4.664435415509631
2000	3.184183732527621
2001	3.8117482670758096
2002	2.9324103015428724
2003	2.9242552668215493
2004	2.132022386668574
2005	1.911777658904836
2006	1.8220522061690534
2007	1.7811096715764578
2008	1.5740732938410589
2009	1.835198228753644
2010	1.389539688354618
2011	1.1086516370655561
2012	1.0117761289574194
2013	0.8042733624058789
2014	0.6782041808228504
2015	0.8542393591161173