Year	% of total
1970	98.7692112704494
1971	98.9138653243408
1972	99.015128098693
1973	99.02810394175529
1974	98.7240999265845
1975	98.48796062616837
1976	98.36990023813011
1977	97.96356694678342
1978	98.02134157740392
1979	97.34862351033799
1980	96.37954237483419
1981	95.34273614183027
1982	95.4229724945789
1983	94.08125535554018
1984	95.62956913923853
1985	94.70586783398092
1986	94.03015167736443
1987	93.58800246612314
1988	93.58025257185038
1989	93.5711453285061
1990	79.56204379562044
1991	79.45205479452055
1992	80
1993	79.39393939393939
1994	79.3103448275862
1995	79.67032967032966
1996	79.58115183246073
1997	79.5
1998	80.28846153846155
1999	80.18433179723502
2000	80.08849557522124
2001	82.5
2002	82.94573643410853
2003	83.39350180505414
2004	83.72881355932203
2005	85.16129032258064
2006	85.35211267605634
2007	81.62291169451073
2008	82.28941684665226