Year	% of cohort
1971	99.3419418334961
1972	99.2969131469727
1973	99.6115112304688
1974	99.0870666503906
1975	99.3369827270508
1976	99.2807998657227
1977	99.5254135131836
1978	99.2627105712891
1979	96.3053512573242
1980	89.3900527954102
1981	82.0006484985352
1982	76.9851608276367
1983	72.8773574829102
1984	69.2987518310547
1985	66.0568695068359
1988	98.4464797973633
1989	45.7444305419922