This study reports the comparative increase in enrollments at each level of education in all 22 member countries of the Organisation for Economic Cooperation and Development between 1950 and 1965. Data are also included for Yugoslavia, an associated member country. The first two chapters deal with enrollment trend analysis -- chapter one being concerned with total enrollments and chapter two with each educational level separately; while chapter three is concentrated more particularly on the incidence of demographic factors on the rise in enrollments. In chapter four, the authors endeavor to extrapolate the trends observed during the period studied up to 1980. The main conclusions drawn from the study are presented in the final chapter. The statistical material used for determining enrollment trends, an examination of the structure of each country's system (together with the changes that have been made since 1950), and certain technical details concerning the extrapolation of the trends observed in chapter four are provided in three annexes to the document. Related documents are ED 057 470, EA 004 323, and EA 004 421-425. (Author/JH)