In China, for example, the share of population of working age has been rising quickly up to now. But between 2010 and 2050, it is expected to decline more quickly than in the United States, and by about the same as in Germany. 6  In theory, ageing can in some circumstances produce lower saving rates.
The reason is that people have a longer period over which compounding affects their wealth, so that they need a lower saving rate each year. See, for example, D. Bloom, D. Canning and M. Moore (2004), ‘The Effect of Improvements in Health and Longevity on Optimal Retirement and Saving', NBER Working Paper No. 10919 (http://papers.nber.org/papers/w10919.pdf).