Part of the reason why people increasingly married their socioeconomic and educational peers was economic in nature. Innovations that became commercially available in the late twentieth century such as the washing machine and frozen food reduced the amount of time people needed to spend on housework, which diminished the importance of domestic skills. Moreover, it was no longer possible for a couple with one spouse having no more than a high-school diploma to earn about the national average; on the other hand, couples both of whom had at least a bachelor's degree could expect to make a significant amount above the national average. People thus had a clear economic incentive to seek out a mate with at least as high a level of education in order to maximize their potential income. A societal outcome of this was that as household gender equality improved because women had more choices, income inequality widened.