Year	% of total
1970	9.373367612221111
1971	9.321133120506481
1972	9.557833047116326
1973	14.83494272060619
1974	14.854197645720072
1975	14.699477421714121
1976	14.261917421214687
1977	13.498389410582881
1978	12.826060076317514
1979	12.790659183275338
1980	12.777941956556859
1981	13.064338847905995
1982	13.183058072797923
1983	13.447785534317944
1984	19.71360936092121
1985	22.59264383384544
1986	21.798587868391756
1987	22.945387418460708
1988	22.783109388170054
1989	22.903293662492572
1990	8.628318584070795
1991	9.023354564755838
1992	9.387755102040817
1993	9.639727361246349
1994	10.018726591760299
1995	10.261026102610261
1996	10.431034482758621
1997	10.587262200165426
1998	10.668789808917198
1999	10.77981651376147
2000	10.834553440702782
2001	10.68917018284107
2002	10.569105691056912
2003	10.423452768729643
2004	10.262828535669586
2005	10.138805069402535
2006	10.098665118978525
2007	9.983361064891847
2008	9.883103081827842