assortative mating is sometimes cited as a source of inequality, as those who mate assortatively would marry people of similar station to themselves, thus amplifying their current station. There is debate, however, about whether this growing preference for educational and occupational similarities in spouses is due to increased preferences for these traits, or the shift in workload that occurred as women entered the workforce. This concentration of wealth in families also perpetuates across generations as parents pass their wealth on to their children, with each successive generation inheriting the resources of both of its parents. The combined resources of the parents allow them to give their child a better life growing up, and the combined inheritances from both parents place them at an even greater advantage than they would be with their superior education and childhoods. This has an enormous impact on the development of the social economic structure of a society. Economics A related concept of 'assortative matching' has been developed within economics. This relates to efficiencies in production available if workers are evenly matched in their skills or productivity. A consideration of this assortative matching forms the basis of Kremer's 1993 O-ring theory of economic development. See also Directional selection Disruptive selection Endogamy Genetic sexual attraction Koinophilia Matching hypothesis Negative selection (natural selection) Reinforcement (speciation) References Mating Sexual selection Fertility