This study examines a 118-year continuous record of retention and graduation rates at a public university for long-term trends not observable in shorter studies. While the first year retention rates stayed level over much of this period, second year rates increased steadily by 1.2% per decade. In contrast, graduation rates at 4 years compared to 6 years declined by 1.9% per decade. Even with large changes in cohort size and composition, these rates demonstrate remarkable stability over long periods, not varying by more than a few percent within narrow ranges. Considered in context with other institutional and student data, the patterns are reminiscent of those exhibited by complex adaptive systems. The state of equilibrium for the last 70 years is attributed to continuing co-adaptation between the capabilities and preparation of entering students and the expectations and requirements of the institution, implying that over the long-term, retention and graduation rates are measures of institutional stability rather than performance. (Contains 8 figures and 1 footnote.)