The Social Mobility Index (SMI) Ranking differs from most other rankings, as it focuses directly on the factors that enable economic mobility and to what extent a college or university educates more economically disadvantaged people (family incomes below the national median) at lower tuition so that they graduate into good paying jobs. The colleges that do the best at this rank higher according to the SMI. The SMI is computed from six variables:

• ethos,
• published tuition,
• percent of student body whose families whose incomes are below $48K (slightly below the US median),
• graduation rate,
• median salary approximately 5 years after graduation,
• endowment. 

Unlike other rankings that assign percentages to variables and then sum for a score, the SMI variables are mathematically balanced against live data so that they fall into three weighting tiers: a) ethos, tuition, and economic disadvantage at the highest tier (access); b) graduation rate and salary at the next, half-weight tier (outcome); and c) the endowment at a half again, or 1/4 weight tier (institutional capability). Each weighting tier is thus twice as "sensitive" as the next in that making realistic changes to the variables at that tier can cause approximately twice as much movement in the rankings.

Enhancing economic mobility means providing access to economically disadvantaged students, graduating them, and moving them into good paying jobs. Each tier constitutes a proxy for one of three concepts: access, outcome, and institutional capability. Considering these tiers in reverse helps explain the intuition behind their weightings. The bigger the endowment a university possesses, the more capability it has to address any problem. Yet because drawdowns on an endowment can be aimed at purposes separate from the problem of economic mobility, endowment primarily serves in the SMI as a tie-breaker. If school A and school B are very close with respect to social mobility policy, yet B has a larger endowment, A is rewarded by the SMI for having applied its resources more efficiently.

Optimizing outcomes is key to economic mobility, hence the heavier weighting in this tier. Yet no matter how many students who graduate and then land good paying jobs, economic mobility is suppressed if tuition in the US continues to ramp unchecked. Students and families cannot advance economically if they must labor under huge debt. And, of course, no matter how high the graduation rate and no matter how high the early career salary, if higher education serves primarily as a finishing school for scions of the privileged, then economic mobility goes unaddressed. That is why the access proxies (ethos, tuition and economic background) are assigned the greatest weighting. Lowering tuition, recruiting more economically disadvantaged students, and promoting social mobility as a value in higher education are the fundamental drivers for improving higher education's contribution to economic mobility.

A high SMI ranking means that a college is contributing in a responsible way to solving the dangerous problem of declining economic mobility in United States. A school with a low SMI is more likely to be failing, sometimes miserably, at providing real opportunity and advancement for the economically disadvantaged citizens of United States. The SMI should serve as a valuable mirror for policy, an instigator of conversations with institutions that are doing a better job, and a stimulant for policy change.