Relative Deprivation
The feeling of disadvantage that comes not from objective lack but from comparison — perceiving that you have less than the people or groups around you, or less than you feel entitled to.
Origin
American sociologist Samuel Stouffer introduced the concept in The American Soldier (1949), a landmark study of U.S. military morale during World War II. Stouffer's team discovered a paradox: army units with the highest promotion rates also had the highest dissatisfaction among those not promoted, because soldiers compared themselves to peers who advanced. The finding showed that perceived deprivation is shaped by social comparison rather than absolute conditions.
Everyday Use
Your salary feels perfectly fine until you learn a colleague earns more for similar work. A neighborhood feels safe until a wealthier one moves into view. Relative deprivation explains why rising prosperity can coexist with rising dissatisfaction — it's not what you have, it's what you have compared to others.