Year	% of cohort
1971	96.7751007080078
1972	97.0769805908203
1973	97.2393569946289
1974	97.9834899902344
1975	98.8552474975586
1976	98.1840133666992
1977	97.9127578735352
1978	98.2875671386719
1979	98.9634780883789
1980	99.0353012084961
1981	96.9552612304688
1982	97.345573425293
1983	96.7901611328125
1984	96.0726776123047