Over the next several decades, it is projected that there will be an unprecedented aging of the population in all developed countries. During this demographic transition, the changing age structure of each of these countries will have macroeconomic consequences. If countries age at different rates, the returns to the factors of production in those countries may diverge. Where this occurs, international capital and labor flows might occur in order to take advantage of these differences. This could take the form of either immigration or international capital flows. Such flows have the potential...