The discrepancy that one perceives between what one has and what one could or should have, in contradistinction to absolute deprivation of the bare necessities for living. Egoistic relative deprivation arises from unfavourable comparisons between one's individual circumstances and those of a comparative reference group, and it tends to generate personal dissatisfaction and unhappiness; fraternal relative deprivation arises from unfavourable comparisons between the circumstances of one's group (social class, racial group, occupational group, and so on) and a reference group, and it tends to generate protest behaviour, rebellion, and in extreme cases revolution. The concept was introduced by the US sociologist Samuel Stouffer (1900–60) and several co-authors in their study of The American Soldier (1949), where it was reported that army units with the highest rates of promotion also had the highest levels of dissatisfaction among those not promoted. The US sociologist Robert K(ing) Merton (1910–2003) developed the idea further in his book Social Theory and Social Structure (1957), arguing that high rates of social mobility raised hopes and expectations and encouraged over-optimistic social comparisons. The British sociologist Walter G(arrison) Runciman (born 1934), in his book Relative Deprivation and Social Justice (1966), provided further evidence that workers' feelings of deprivation and class consciousness tend to be relative rather than absolute. Subsequent researchers have generally corroborated and extended these basic ideas and findings. See also equity theory, social comparison.