At approximate five-year intervals, the ISM consulting staff conducts an internal study designed to identify those variables that are associated most strongly with a private-independent school’s ability to sustain excellence in its student programs. The outcome list, termed the ISM Stability Markers®, changes moderately from one iteration to the next, in part because North American economic and enrollment-demand conditions tend to shift over time, and in part because ISM’s capacity to measure—and, thus, to detect—prominent markers gains strength steadily with enhancements in the organization’s internal research capabilities. The second iteration, published in 2001, comprised two tiers, the first with eight items listed in rank order and the second with nine more items that were not prioritized. This new iteration also comprises two tiers, with six items in the top tier and 12 unranked items in the second.