At a 2-year horizon, an MBA is associated with an increase of roughly 16% of a standard deviation in accuracy. At a 3-year horizon, the increase is roughly 30% of a standard deviation. The results are consistent with an MBA as a proxy for heightened expertise: analysts with an MBA are more likely to disagree with other analysts contemporaneously rating the same firm and are less likely to inflate ratings. Moreover, these ratings more often prove accurate predictors of future movements in credit spreads, particularly over longer horizons for which forecasting is likely to require greater skill.
--Cesare Fracassi, Stefan Petry, and Geoffrey Tate on evidence that an MBA might not be so useless after all