Year	% of total
1970	89.40963647646555
1971	89.37239606525523
1972	88.85155925736615
1973	87.84155151562383
1974	87.49777022900523
1975	87.91447260552675
1976	87.73147558310188
1977	87.94200821789032
1978	87.65627668348873
1979	87.2865646166424
1980	87.05038354538233
1981	86.50690144423329
1982	86.88058432901202
1983	86.50205520351626
1984	86.0898085495258
1985	85.57085927753691
1986	86.26327278130206
1987	87.07597403471748
1988	86.30301804321364
1989	86.66026243356112
1990	77.87418655097615
1991	76.875
1992	75.86206896551724
1993	75.04873294346979
1994	73.86363636363636
1995	72.62569832402235
1996	72.66313932980599
1997	71.35231316725978
1998	69.94633273703042
1999	70.71547420965058
2000	71.95121951219512
2001	69.5024077046549
2002	66.72268907563024
2003	63.652482269503544
2004	66.40127388535032
2005	66.35802469135803
2006	66.46616541353384
2007	64.03785488958991
2008	65.06024096385542