Year	% of total
1970	91.09962329661218
1971	91.21116386770521
1972	91.33682597934738
1973	91.20061821416145
1974	91.84981654030373
1975	91.95576566783573
1976	91.85294223814826
1977	91.35297875060961
1978	91.7209202425342
1979	91.74361996725244
1980	91.41987408243403
1981	91.9471604111304
1982	91.7555709397853
1983	91.8005376300141
1984	92.0320905474298
1985	92.11497483984174
1986	91.7305239943785
1987	91.51295839625615
1988	91.62131053230944
1989	91.44662941503772
1990	96.37096774193549
1991	96.53049804141018
1992	96.77083333333333
1993	96.98019801980197
1994	97.13345864661655
1995	97.21964782205747
1996	97.38475177304964
1997	97.41602067183463
1998	97.54801798120147
1999	97.59036144578313
2000	97.76345716451857
2001	97.30753050063105
2002	97.22991689750693
2003	97.09414955443626
2004	96.90839694656489
2005	96.88758696448187
2006	96.46601941747572
2007	96.49507119386638
2008	96.27031019202363