Year	% of total
1970	85.98793425129895
1971	85.3886825296322
1972	82.261191158813
1973	82.79045705920058
1974	82.51576111161535
1975	83.34999066183047
1976	82.88639491945361
1977	81.96774426036737
1978	80.8986985925098
1979	80.14178407830656
1980	79.99198076595422
1981	79.3217752605778
1982	79.5205286351821
1983	78.26642621038306
1984	77.60837262133387
1985	76.16075174437053
1986	72.93818973671765
1987	73.93838924573551
1988	74.18973102454909
1989	73.87512891931497
1990	83.38461538461537
1991	84.80243161094225
1992	85.625
1993	86.5625
1994	86.95652173913044
1995	88.56209150326796
1996	89.36170212765957
1997	90.25069637883009
1998	90.97938144329896
1999	91.56626506024097
2000	90.33149171270718
2001	88.81987577639751
2002	90
2003	90.10416666666666
2004	90.02624671916011
2005	90.17632241813602
2006	83.74384236453201
2007	78.11764705882352
2008	75.15657620041753