Relative deprivation, a concept central to reference group theory, was developed by Robert K. Merton. It explains how people feel deprived when they compare themselves to a reference group and perceive a discrepancy between their actual and expected conditions. Karl Marx discussed exploitation (not relative deprivation), Max Weber focused on class/status/party (not relative deprivation), and Durkheim's suicide theory focused on social integration (not deprivation comparisons).