Year	% of total
1970	2.8636747040771593
1971	2.629449267506254
1972	2.596974762239123
1973	2.506778371269568
1974	2.092401266613954
1975	2.2041162318934413
1976	2.404802486626444
1977	2.388516628104411
1978	2.504618815237556
1979	2.465662330534377
1980	2.9837686332826463
1981	2.744673007547984
1982	3.0145216504463637
1983	2.926585245071759
1984	2.675362404265254
1985	2.797364552623183
1986	2.959780084777274
1987	2.5757868616321438
1988	3.3918918383460026
1989	3.7282183106952376
1990	2.2006472491909386
1991	2.307692307692308
1992	2.488832163369496
1993	2.7414330218068534
1994	2.982233502538071
1995	3.313840155945419
1996	3.587736464448793
1997	3.64963503649635
1998	3.796610169491525
1999	3.724137931034482
2000	3.9886039886039883
2001	4.256908140403286
2002	4.520654715510522
2003	4.498816101026046
2004	4.360902255639098
2005	4.374057315233785
2006	4.324734446130501
2007	4.953031596925705
2008	7.290400972053463