relative impact on student outcomes of changing incoming student credentials versus effectiveness in the allocation of resources within public higher education. She finds that the former has a smaller impact than the latter. Similarly, studies have usefully shown how tuition and aid policies affect student performance as measured partially by these statistics. The range of performance metrics, including a discussion of the meaning of graduation rates as calculated by the Integrated Postsecondary Education Data System (IPEDS), is described in detail in Appendix A.

While their role is accepted, the measures identified above should not be confused with productivity as defined in this report. Used as accountability tools, one-dimensional measures such as graduation rates and time-to-degree statistics can be abused to support misleading conclusions (e.g., in making comparisons between institutions with very different missions). Also, because graduation rates are strongly affected by incoming student ability, using them in a high-stakes context may induce institutions to abandon an assigned and appropriate mission of broad access. Use of these kinds of ratio measures may similarly induce institutions to enroll large numbers of transfer students who are much closer to earning a degree than are students entering college for the first time, whether that is the supposed mission or not.

To illustrate the ambiguity created by various metrics, student-faculty ratio levels can be linked to any combination of the following outcomes:

Low Student-Faculty Ratio

High Student-Faculty Ratio

low productivity

high productivity

high quality

low quality

high research

low research

resource diversion

unsustainable workload

The ability to distinguish among these outcomes is crucial both for interpreting student-faculty ratios and for policy making (both inside and outside an institution).

Time to degree, graduation rate, and similar statistics can be improved and their misuse reduced when institutional heterogeneity—the mix of full- and part-time students, the numbers of students who enter at times other than the fall semester, and the proportion of transfer students—is taken into account. Additional refinements involve things like adjusting for systemic time-frame differences among classes of institutions or students. A ratio measure such as a graduation rates that is lagged (allowing for longer time periods to completion) is an example. To avoid the kinds of overly simple comparisons that lead to misguided conclusions—or, worse, actions—responsible use of performance metrics (including productivity if it is used for such purposes) should at the very least be used only to compare outcomes among like types of institutions or a given institution’s actual performance with expected levels. The institutional segmenta-

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