Horizontal inequality is the inequality—economical, social or other—that does not follow from a difference in an inherent quality such as intelligence, attractiveness or skills for people or profitability for corporations.
Traditional economic theory predicts that horizontal inequality should not exist in a free market.
Even in simulated systems, inequality of perfectly identical actors arises, to give "the rich and poor".
[2] There are three main causes of horizontal inequality; overt discrimination, exclusivity of public goods, and unequal access to resources.
[3] Disadvantaged cultural groups may react together, in the form of protests or riots over their collective situation.