This is of course an over-simplification and use of either index or both should be done with much care. For example, CPI reflects prices paid by urban consumers and the basket of goods has not been rigidly fixed. HEPI components are apparently fixed and reflect higher education spending patterns in 1972. Please note that while a description of the Research and Development Price Index is included, it is very nearly perfectly correlated and equal in magnitude to HEPI due the high degree of overlap in components. In other words, it is redundant as a higher education index.
Several cautions are applicable.
That said, median income for a Missouri family of four is a robust statistic that has high public acceptance and frankly, any statistic has similar limitations when government programs, modern family structures, and parental financial responsibility patterns are considered. As stated in the introduction to this section, annual change in HEPI has outpaced CPI since about 1982. In other words, the price of higher education has increased more rapidly than the price of other consumable goods and services - Higher education has become more expensive. This pattern is shown in Table 2 and the two associated graphs Figures 2 and 3. There is no a priori reason to use 1983, it is simply and commonly accepted practice.