The Carnegie Classifications were designed 50 years ago to help researchers, policy makers and college officials themselves make sense of the complex, diffuse mélange of roughly 4,000 American colleges and universities whose missions, resources and student bodies vary greatly. That the Carnegie framework has, for many people inside and outside higher education, become reducible to one factor is among the reasons why officials at the American Council on Education, which last year joined the Carnegie Foundation for the Advancement of Teaching in managing the classifications, concluded that it needed an overhaul.