Year	% of cohort
1974	69.9594268798828
1975	68.6132125854492
1976	71.7051086425781
1977	66.7147521972656
1978	65.4233932495117
1979	68.1741409301758
1980	69.5244903564453
1981	71.91943359375
1982	55.2821998596191
1983	66.7559661865234
1984	68.4523010253906
1985	72.9304122924805
1986	74.5242385864258
1987	75.7420806884766