Year	% of total
1971	6.5722659365108616
1972	7.342672339211089
1973	7.462250316454995
1974	7.181959554601872
1975	7.032217226459454
1976	5.856478266695807
1977	6.045924126989241
1978	5.728548775448717
1979	6.373888382685819
1980	6.922531169104904
1981	6.3563600039790655
1982	6.902772546486766
1983	7.4182540581551955
1984	7.618740469861779
1985	7.389122097032352
1986	6.830071755143609
1987	6.8453295124415865
1988	6.557985603409899
1989	6.2582998162641745
1990	6.193323160230491
1991	6.1288309056001165
1992	7.033078825656931
1993	7.0094202504656575
1994	7.010863044122696
1995	7.10380315986878
1996	8.286659672267051
1997	8.518275465528871
1998	7.915570205824476
1999	8.490785853901073
2000	9.108363377516966
2001	8.321697552380272
2002	8.036312570033806
2003	6.443630841089726
2004	5.967332170385711
2005	6.0321793819534895
2006	6.31670145029041
2007	6.488570561643405
2008	6.548869256068862
2009	6.350020974886908
2010	5.626609701838784
2011	5.4584762295493645
2012	5.437038150526495
2013	5.318985554717733
2014	5.033613380801594
2015	4.809903410875814