Year	% of total
1970	89.42298318079376
1971	89.29580847657861
1972	88.90078168034299
1973	88.1342089736504
1974	87.96526249036155
1975	87.02598943033234
1976	87.17738703187867
1977	85.47962264707836
1978	85.8277503471258
1979	85.44969798449186
1980	85.64556499591836
1981	84.42701955476402
1982	80.77989806387014
1983	81.46713712142366
1984	80.63667761101925
1985	81.43932624714152
1986	82.55513498177967
1987	82.38502505428931
1988	79.84703279363735
1989	78.89212673073975
1990	88.32565284178187
1991	87.89308176100629
1992	86.64383561643835
1993	85.71428571428571
1994	82.38095238095238
1995	81.22866894197952
1996	82.87037037037037
1997	82.80060882800609
1998	83.23442136498517
1999	83.73751783166904
2000	83.85269121813032
2001	83.68200836820083
2002	84.0909090909091
2003	83.88814913448735
2004	84.21052631578947
2005	84.7001223990208
2006	85.06417736289382
2007	83.68617683686178
2008	83.53808353808354