Year	% of total
1970	86.63023127753304
1971	86.51842278031302
1972	85.59706303110559
1973	85.39691511260303
1974	84.83801904787536
1975	84.8283779681991
1976	84.67598004338144
1977	84.3354523576664
1978	84.64908178096641
1979	85.34320373087402
1980	85.34420264947538
1981	83.91003072268997
1982	83.44550798222457
1983	82.84802687893415
1984	82.8328278834639
1985	81.08396089174266
1986	81.7889617593976
1987	82.49962701825812
1988	81.06813932927037
1989	80.73149816332297
1990	83.75136314067612
1991	83.73860182370821
1992	83.76694759985342
1993	83.50298350298351
1994	82.78145695364239
1995	81.11324376199616
1996	81.07196401799101
1997	81.09619686800895
1998	82.01208674013508
1999	82.15811965811966
2000	81.89717595944967
2001	81.17505995203837
2002	80.8359621451104
2003	80.32036613272311
2004	79.76726726726727
2005	79.55801104972376
2006	76.64233576642336
2007	76.36298421807749
2008	74.94313874147082