Year	% of total
1970	69.02978398366942
1971	68.42777863564291
1972	68.15232296930276
1973	63.1605986445783
1974	65.20056718719493
1975	65.49264073326763
1976	66.5460326961722
1977	66.43172566011066
1978	68.03862415269862
1979	68.96624301377305
1980	71.8101878275173
1981	71.16033237921617
1982	71.53299458262487
1983	71.92050419284456
1984	70.23613003520643
1985	69.72060321502465
1986	70.9454560361791
1987	72.2299372909699
1988	75.01422223233311
1989	73.8280890339196
1990	87.01298701298701
1991	86.32707774798928
1992	86.31578947368422
1993	85.36585365853658
1994	86.29441624365482
1995	86.79245283018868
1996	86.6822429906542
1997	86.40552995391705
1998	86.22222222222223
1999	85.77777777777777
2000	85.03401360544217
2001	83.99014778325123
2002	85.26077097505669
2003	86.10526315789474
2004	86.41975308641975
2005	87.78195488721805
2006	87.80918727915194
2007	87.3015873015873
2008	85.87786259541986