Year	% of total
1970	9.69086476161431
1971	13.027501302245948
1972	12.492395430108875
1973	10.51623962790249
1974	16.85586491747811
1975	18.123551457288183
1976	20.505187807887594
1977	16.798282200798702
1978	19.252479220311898
1979	22.179415649145362
1980	20.12055528410247
1981	20.358876429109802
1982	22.713868932889905
1983	21.267177175914036
1984	34.69278792266121
1985	35.921929822442245
1986	37.78410046923016
1987	33.5801838850972
1988	39.450877566476436
1989	47.30355345657912
1990	51.19266055045871
1991	52.045944005743
1992	52.45730219588707
1993	52.63335584064821
1994	52.64187866927593
1995	53.23970635173955
1996	53.565867331049525
1997	53.73179611650486
1998	54.14315414315415
1999	54.58515283842795
2000	54.73145780051151
2001	54.928790840547336
2002	54.70155355682748
2003	54.45360276522202
2004	54.119170984455955
2005	53.96704689480355
2006	53.0306809678224
2007	51.755241345685036
2008	51.03514684641309