Year	% of total
1970	84.58970062935873
1971	82.90873488745308
1972	83.74123244056433
1973	85.02613202730883
1974	82.1527578681302
1975	80.18961395295602
1976	77.36991286500323
1977	80.98220219787015
1978	82.44156242055962
1979	80.92342448738005
1980	82.12211393273851
1981	81.55188736405223
1982	82.33562591694673
1983	85.50035696326694
1984	83.61704499425527
1985	82.80024521824424
1986	83.91035830487645
1987	85.31741622744585
1988	84.09348998422786
1989	82.98662419136379
1990	90.3448275862069
1991	89.8989898989899
1992	89.62264150943396
1993	89.32926829268293
1994	88.65030674846625
1995	88.69565217391305
1996	88.79781420765028
1997	88.3008356545961
1998	87.64367816091954
1999	88.37209302325581
2000	86.79775280898876
2001	85.50295857988166
2002	85.43417366946778
2003	85.56149732620321
2004	85.42199488491049
2005	84.71502590673575
2006	85.74821852731591
2007	86.17511520737328
2008	86.0091743119266