The approach taken in these studies is largely a-theoretic. More specifically, they implicitly model the demand for assets as being a function of only current demographics. Unless investors are completely myopic, however, the expected rate of return on investments will be a further determinant of how much people want to invest. Thus there will a feedback from the future path of stock prices back to the pattern of investment. And future stock prices will in turn be influenced by future demographics. Dealing with these considerations requires the construction of a general equilibrium model with an explicit formulation of expectations
