Year	Percent
1971	0.83931
1972	0.84343
1973	0.85234
1974	0.85275
1976	0.87303
1977	0.88315
1978	0.88601
1979	0.8937
1980	0.91115
1981	0.91153
1982	0.91196
1983	0.91446
1984	0.91925
1985	0.92681
1986	0.92483
1987	0.93764
1988	0.93913
1989	0.97272
1994	0.9769
1995	0.95951
1996	0.97523
1997	0.96719
1999	0.97035