Year	% of total
1970	80.24079741286792
1971	79.34101019509899
1972	78.71193422195721
1973	78.83538822780277
1974	77.15714737307961
1975	77.63940010317637
1976	76.47772151644891
1977	76.1903990325316
1978	76.4719598542015
1979	78.84564861688663
1980	78.4970795701461
1981	77.5404775507613
1982	77.92014152244363
1983	77.82139245333067
1984	75.46298887889621
1985	76.44023334063353
1986	75.24278014064933
1987	75.16678257545254
1988	74.45576941728312
1989	73.60464477410088
1990	81.25
1991	82.6530612244898
1992	82.10526315789474
1993	82.41758241758241
1994	81.60919540229885
1995	81.81818181818183
1996	81.70731707317073
1997	81.3953488372093
1998	83.33333333333334
1999	83.50515463917526
2000	83.83838383838383
2001	83.80952380952381
2002	84.54545454545455
2003	84.87394957983193
2004	85.03937007874016
2005	85.82089552238806
2006	86.3013698630137
2007	86.36363636363636
2008	87.03703703703704