This publication consists of three papers that deal with the statistical evaluation of the inschool and out-of-school population of UNESCO member nations from a purely demographic viewpoint. Particular attention is devoted to the statistical aspects of measuring school retardation, the age structure of the enrolled and not-enrolled population, and the use of enrollment ratios and intake rates for measuring school participation for different age groups. The studies have the dual purpose of publishing raw data of the age distribution of inschool and out-of-school youth, as well as providing statistical analyses and projections based on these data. The individual papers include "A Statistical Analysis of Age Data and the Measurement of School Retardation," by P. Bernard; "School Enrolments and Demographic Structures," by D. Blot; and "Employing Enrolment Ratios and Intake Rates for Developing Countries: Problems and Shortcomings," by B. Fredriksen. (JG)