Question: How can increased human capital accumulation which results in a higher average number of years of education contribute to sustaining a high rate (i.e., percentage change) of economic growth over time? What specific positive externalities might be expected from workers with more education interacting with other workers with education or even with workers with little education? Can you see how two (or more) workers might be more productive together than they would be if they did not interact? Can you give some concrete examples of how and when such interaction have resulted in such positive externalities? (One example: Have you ever studied with someone else? Can both learn more by such sharing than by studying alone? Is this a positive externality, i.e., a spillover effect?)