Year	% of total
1970	81.63299704405796
1971	80.91432900106686
1972	80.60077243872877
1973	78.65898505401194
1974	77.74848379041013
1975	77.43029166990169
1976	78.21848145071479
1977	80.17155648218889
1978	75.46837603391859
1979	71.2849685665763
1980	72.71931241710095
1981	71.95248025990362
1982	76.51914401461998
1983	78.4143570536829
1984	72.02443107284276
1985	69.53039373058175
1986	70.27891981022911
1987	71.29356996096762
1988	71.27097217612489
1989	71.9432422754246
1990	77.00787401574803
1991	79.62328767123287
1992	82.71375464684016
1993	85.55798687089715
1994	90.39408866995073
1995	89.38271604938272
1996	88.14814814814815
1997	88.67469879518072
1998	88.55721393034825
1999	88.12664907651715
2000	88.23529411764706
2001	88.68894601542416
2002	87.84530386740332
2003	87.05882352941177
2004	87.14285714285714
2005	86.62613981762918
2006	87.28323699421965
2007	87.7840909090909
2008	87.98882681564247