Year	% of total
1970	60.451197930440706
1971	60.74150441972112
1972	60.45406129586599
1973	59.47891947431052
1974	58.813446888698806
1975	58.876039276229285
1976	58.22343861315602
1977	58.6264330971484
1978	59.22451935985613
1979	59.197194541244045
1980	61.001626864329076
1981	62.59530457199962
1982	65.01279095210079
1983	65.52300016254752
1984	66.36757364585645
1985	67.58946485268486
1986	68.94545886254619
1987	69.73398058252427
1988	69.65068557209729
1989	69.56375720832239
1990	93.09360730593608
1991	92.72727272727272
1992	91.50726855394032
1993	91.7981072555205
1994	92.35245220282626
1995	92.67059814658803
1996	92.43697478991596
1997	92.37217099748533
1998	92.15189873417722
1999	92.19677692960136
2000	92.0103092783505
2001	87.27569331158239
2002	92.67202859696158
2003	93.00087489063867
2004	93.04721030042919
2005	93.16666666666666
2006	93.41894060995185
2007	93.26298701298701
2008	93.60374414976599