The purpose of this paper is to clarify the knowledge used in university education. I focus on the relationship between time and knowledge, and attempt to clarify the rate of change about knowledge used in university education.

To provide a basis for empirical analysis, I have evaluated various textbooks used in universities, focusing on the entries in the indexes found at the end of the textbooks. I create two indexes, to estimate the rate of change of the knowledge in a discipline. In order to compare the rate of change among disciplines, I selected two fields- physics and economics; in economics again I selected two areas -micro-economics and macroeconomics; and in macro-economics. I selected two textbooks written by different authors.

The findings of this paper are as follows. 1) The rate of change in physics exceeds that in economics. 2) The rate of change in macro-economics nearly equals that in micro-economics for the same author. 3) In macro-economics, the rate of change in one textbook does not equal that in the other, but this difference is not more than the difference between disciplines.