economic activities that are not included in market prices, such as pollution. These are negative externalities. However, there are also positive externalities – that is, positive effects of which someone can benefit without having to pay for it. Education bears with it major positive externalities: giving one person more education raises not only his or her output but also the output of those around him or her. Educated workers can bring new technologies, methods and information to the consideration of others. They can teach things to others and act as an example. The positive externalities of education include the effects of personal networks and the roles educated workers play in them. Positive externalities from human capital are one explanation for why governments are involved in education. If people were left on their own, they would not take into account the full social benefit of education – in other words, the rise in the output and wages of others – so the amount they would choose to obtain would be lower than the social optimum. Demand for education Liberal approaches The dominant model of the demand for education is based on human capital theory. The central idea is that undertaking education is investment in the acquisition of skills and knowledge which will increase earnings, or provide long-term benefits such as an appreciation of literature (sometimes referred to as cultural capital). An increase in human capital can follow technological progress as knowledgeable employees are in demand due to the need for their skills, whether it be in understanding the production process or in operating machines. Studies from 1958 attempted to calculate the returns from additional schooling (the percent increase in income acquired through an additional year of schooling). Later results attempted to allow for different returns across persons or by level of education. Statistics have shown that countries with high enrollment/graduation rates have grown faster than countries without. The United States has been the world leader in educational advances, beginning with the high school movement (1910–1950). There also seems to be a correlation between gender differences in education with the level of growth; more development is observed in countries that have an equal distribution of the percentage of women versus men who graduated from high school. When looking at correlations in the data, education seems to generate economic growth; however, it could be that we have this causality relationship backwards. For example,