“Individual Desirability / Aggregate Desirability = Your Desirability Ratio
The higher a relationship’s Desirability Ratio, the more stable a relationship will be. If a relationship’s Desirability Ratio drops below one for either partner, the relationship becomes very likely to dissolve.
To put that in other words: When your partner is much more desirable to you than their “league” would suggest, and when this dynamic is mutual (i.e., each partner values the other more than society on average values that other partner), your relationship will be uniquely stable. However, if either partner values the other less than that person would be valued on an open market, the relationship becomes unstable.”
―
Malcolm Collins,
The Pragmatist's Guide to Relationships