Ric is right about the relevance of growth literature to this discussion. Any country, rich or poor, where the marginal product of capital is below the sum of the rate of depreciation and the population growth rate has over-accumulated capital and is "dynamically inefficient". Diamond's 1965 AER article shows that this is possible in a competitive economy under laissez-faire--no "frictions" other than finite lives are necesssary. A dynamically inefficient economy can be Pareto-improved by drawing off "productive saving" into unproductive forms--fiat money, perpetually rolled-over government debt, pay-as-you-go social security--reducing the capital stock and raising steady-state consumption. This possibility is the long-run analogue of the Keynesian "paradox of thrift": the economy really is over-saving, although it is not at all an aggregate demand problem--it's a missing markets problem due to the "friction" of finite lives (in the long run we're all dead and the unborn aren't around to trade today!). The remedies sound pretty Keynesian, too.