Year	% of cohort
1971	99.5521697998047
1972	99.6322784423828
1973	99.68408203125
1974	99.7938232421875
1975	99.7401962280273
1976	99.68115234375
1977	99.7689819335938
1978	99.7732620239258
1979	99.4982681274414
1980	99.7701797485352
1981	99.7998886108398
1982	99.8275833129883
1983	99.7809906005859
1984	99.8411712646484
1985	99.8065185546875
1986	99.8746490478516
1987	99.8704605102539
1988	99.8454132080078
1989	99.8457183837891
1990	99.8875427246094
1991	99.9430236816406
1998	99.9592590332031