Year	% of total
1970	97.31139336656642
1971	96.85217306630025
1972	96.83794396239989
1973	96.81375890663698
1974	96.90151202932562
1975	95.88781539443177
1976	95.61753834749132
1977	96.14203874329125
1978	96.07635282554983
1979	96.36750078934567
1980	96.16867397220885
1981	95.17907256137252
1982	94.74096040472304
1983	94.35801825895568
1984	93.85246795184105
1985	93.66744357378225
1986	93.83027812365286
1987	93.903165324913
1988	93.43051261447881
1989	93.60677349400675
1990	92.5601750547046
1991	92.75053304904051
1992	92.40780911062907
1993	92.152466367713
1994	91.8918918918919
1995	91.42212189616254
1996	90.69767441860465
1997	90.0709219858156
1998	90.15317286652079
1999	89.6328293736501
2000	90.15748031496062
2001	89.34426229508196
2002	87.61467889908256
2003	87.71551724137932
2004	87.73388773388774
2005	88.29174664107485
2006	89.103690685413
2007	88.03738317757009
2008	85.8719646799117