Year	% of total
1970	2.9545029249121457
1971	2.999900200087182
1972	3.0085484390508337
1973	2.8064528917019897
1974	2.7658911891717075
1975	2.7948538513996612
1976	2.8291587124528164
1977	2.613347080511018
1978	2.624663929012674
1979	2.528052003486939
1980	2.403504113308277
1981	2.307376833082986
1982	2.144155582687012
1983	2.134943980001268
1984	2.533223868571297
1985	2.7676559572587323
1986	2.6610101583925165
1987	2.5739977107585568
1988	2.6167531508636976
1989	2.657239613389624
1990	4.790419161676647
1991	4.678362573099415
1992	4.678362573099415
1993	4.761904761904762
1994	4.848484848484849
1995	5.194805194805195
1996	4.49438202247191
1997	4.371584699453552
1998	4.81283422459893
1999	5.357142857142857
2000	6.289308176100629
2001	7.4324324324324325
2002	7.482993197278912
2003	7.547169811320755
2004	8.724832214765101
2005	8.974358974358974
2006	8.860759493670885
2007	8.982035928143713
2008	8.522727272727272