Movements between grades of a social process, for example an educational process, can be described by transition probabilities. In the educational system dropouts run counter to educational goals. Here consequences of dropouts on length of stay in school and the cost of education are examined for the two sexes. On application to Nigeria, the average length of stay is found to be small, 4‐1 years for boys and 3‐8 years for girls instead of the statutory six years. Completion costs are considerably lower because of high dropout rate. The average completion cost for a child in grade one is N 28‐7 for boys and N 26‐6 for girls instead of N 42‐00 in each case (N l.00 = £05).