Particularly in the developing countries, a considerable reserve of unutilized intellectual ability exists. Surveys show that even in developed countries those enrolled in secondary education or university studies are not necessarily more able than others in their group who do not continue their education. It may be that only a fraction of the population able to benefit from higher education actually does so. For example, proportionately more workers and more girls benefit from higher education in socialist eastern Europe than in the advanced countries of the West, yet there is no reason to suppose that actual ability for such groups varies between regions. The price mechanism may also intervene where normally demand would exceed educational supply, and the poor-but-able are denied further education. The capacity to succeed in studies at a given level obviously depends on intellectual ability, and this is what is measured, but it depends also on determination and perseverance. In terms of development and considering high youth unemployment, the absence of educational opportunities which would encourage and pay students to study leads to the lack of utilization of a vast amount of human intellectual potential.