The size and growth of higher education tend to be defined by the share of persons enrolling, or the entry rate, of those of traditional college age. Entry rates were around 5% on average in the economically advanced countries in the 1950s and surpassed 50% on average in the early years of the 21st century.

Over the years, however, the definitions changed in international statistics. While university education was addressed up to the 1960s, subsequent reports began to use the term higher education with greater frequency, indicating that institutions that did not play a formal role in research still had much in common with those that did. In the 1980s, UNESCO and OECD, the major compilers of education statistics, moved toward using the term tertiary education, ...