The Federal Reserve Bank of San Francisco (FRBSF) recently published a very interesting study on the relationship between the demographic trends in the United States and equity market performance (find the complete research here).
The research shows that there is a high correlation between the price-earnings ratio (P/E) of U.S.-listed companies (red line on this chart) and the proportion of 40 to 49 year-olds versus the proportion of 60-69 year olds in a population (called in the study the M/O ratio). The study suggests that the ratio between the middle-age population cohort, or citizens accumulating wealth, to the old-age cohort, or citizens spending their wealth in retirement, explains about 61% of changes in P/E ratios in a given period. That is, U.S. equity values are closely related to the age distribution of the population.
See Figure 1: P/E and M/O Ratio Source: FRBSF Economic Letter: "Boomer Retirement: Headwinds for U.S. Equity Markets?" Aug 22, 2011
The study goes even further than this conclusion. It uses information on current U.S. demographic trends to build an outlook for changes in P/E ratios for U.S. equities. This relationship is illustrated here.
See Figure 2: Projected P/E Ratio from Demographic Trends Source: FRBSF Economic Letter: "Boomer Retirement: Headwinds for U.S. Equity Markets?" Aug 22, 2011
According to the model used by the San Francisco Fed, P/E ratios should fall consistently from approximately 15 basis points, where they stood in 2010, to about 8.4 basis points in 2025 and eventually edge up to 9.2 basis points by 2030.
The study uses this projection to estimate future equity prices. It assumes that growth in U.S. corporate earnings will occur at the same pace as it has between 1954 and 2000. These corporate earnings expectations (the denominator of the P/E formula) together with the projected P/E ratio changes allow the authors of the study to extrapolate a future U.S. share prices forecast (the numerator of the P/E ratio formula). The study suggests that U.S. equity markets could see a cumulative fall of 13% between 2010 and 2021. The same figure in real terms, taking into account the impact of inflation, would be 20%, assuming an annual inflation rate of 2%.