This paper applies a two good, multi-region Ramsey-Solow model of the world economy to determine the impact that alternative world fertility rates would have on international capital markets and living standards. Notable features of the model include: relative consumption demands and relative employment efficiencies that vary by age, traded and non-traded goods, vintage technology, outward-looking reference consumption, a proportion of non-optimising rule-of-thumb consumers and imperfect capital mobility due to asymmetric information. The model suggests that projected demographic change will imply a flow of international capital from the ageing regions to the younger regions; and that the world interest rate will fall. The lower world interest rate will cause a loss in living standards for ageing regions, the lenders, and a gain for the younger regions, who are borrowers.