Year	% of cohort
1974	71.0734481811523
1975	67.9937973022461
1976	72.5928421020508
1977	68.5500793457031
1978	67.8844223022461
1979	69.6691665649414
1980	72.3173217773438
1981	74.4462890625
1982	60.3652305603027
1983	69.3124923706055
1984	71.417839050293
1985	75.2500762939453
1986	76.8083190917969
1987	77.7763595581055