Year	% of total
1971	4.748683364025749
1972	5.484276949508141
1973	5.21431156926598
1974	5.847253542999636
1975	5.76895036077483
1976	4.93331438476807
1977	5.562516636473645
1978	5.344819751070038
1979	5.615089311009894
1980	6.082742888169679
1981	5.897901716718277
1982	5.099534245865887
1983	4.576442205882378
1984	4.461891657716078
1985	4.8299385438037445
1986	4.144675394635513
1987	4.402302719311143
1988	5.079512239740622
1989	4.72201268059157
1990	6.940894920951048
1991	8.227823772205056
1992	7.532730653330767
1993	8.232952356491587
1994	8.951766339281122
1995	9.86161929231728
1996	9.64465923324817
1997	9.690666257291985
1998	10.551519351159305
1999	10.663724143306732
2000	9.345138680544562
2001	9.200023744942783
2002	9.177391769834825
2003	7.468631834131902
2004	9.398585876977366
2005	10.367940397393674
2006	9.502913808183953
2007	8.193397986608133
2008	8.802549863911755
2009	9.800293737567975
2010	11.463702428925599
2011	7.958415072962453
2012	7.879824195842051
2013	9.911898546444577
2014	10.671159302578598
2015	9.133111616880853