The source of title restriction is the proportional restriction of title structure, and the fundamental purpose is to avoid title expansion. Take college teachers as an example. In China's university career establishment system, teachers belong to professional and technical posts. The state has strict restrictions on the proportion of senior, deputy senior, intermediate and junior titles in professional and technical posts from high to low. Proportion control is slightly different among provinces, cities and schools, but it basically ensures that the title structure is always pyramid-shaped, which ensures the scarcity and effectiveness of senior titles to some extent.

Today, although the professional titles of different schools cannot be compared horizontally, the professional title system of the same university is still classified vertically.