Does Inequality Have Momentum? The Implications of Convex Inequality Regimes for Mortality Dynamics

For decades, educational inequalities in mortality have widened and mortality among the least educated has stalled, even as overall mortality has improved and an increasing proportion of young people have completed secondary and tertiary education. While researchers recognize that these trends are in part related to changing selection into education groups, there has been no unifying framework for understanding why the trends may be related. This article provides a unifying framework by introducing a concept called the "convex inequality regime," a diminishing returns relationship between relative education and mortality. In populations where convex inequality regimes prevail, even without any changes in the institutions governing inequality or any changes in overall mortality conditions, education transitions result in an increase in mortality for the less educated and an increase in mortality inequality between education groups. The model also shows that lifespan variation increases for lower education groups because convex inequality regimes tend to increase relative mortality more rapidly at younger ages during an education transition. Even after an education transition is complete, inequality between education groups will continue to increase for decades due to the momentum of inequality, a cohort replacement phenomenon where younger, more unequal cohorts replace older, more equal cohorts.