This paper develops a tractable two-country model with life-cycle structure to investigate analytically and quantitatively three potential determinants of the U.S. external imbalances in the last three decades: productivity growth, demographic factors, and fiscal policy. The results suggest that (1) productivity growth differentials are the main driving force at high frequencies, (2) the different evolution of demographic factors across countries accounts for a large portion of the long-run trend, and (3) fiscal policy plays, at best, a minor role. The main prediction of the analysis is that among industrialized countries, capital should generally be expected to flow toward relatively young and rapidly growing economies. In addition, the paper shows that international demographic trends might be partly responsible for the recent declining pattern of the world real interest rate and therefore shed new light on the real side of the interest rate conundrum.
external imbalances, demographics, world interest rate