The Determination of Equity Prices

Drawing on Chs. 4 and 5 (which discuss the supply and demand for securities separately), this chapter investigates whether economics has anything helpful to say about the prices of shares and related securities by reviewing the most important ideas suggested by economic theory in this area and assessing their usefulness in the real world. In the first two sections, two fairly ancient but still popular models of equity (share) prices are examined, one of which (the steady growth model) views shares as claims to future dividends and the other (the asset model) views them as claims to the underlying net assets (corporate net worth). For the most part, these models look at the shares of individual companies in isolation, not at the market as a whole, and that is their weakness, but the asset model in particular provides important insights into aggregate equity values; as an aside to this discussion it is shown that aggregate dividends have the intriguing feature of being an approximately constant percentage of national income, which means that corporate equities offer protection (though not perfect protection) against inflation as well as participation in the real growth of the economy. The third section looks at the Capital Asset Pricing Model (CAPM) – a discovery of the 1960s that, by considering equities in relation to each other, provided important new insights into the relation between risk and return. A more recent alternative approach known as Arbitrage Pricing Theory is discussed next, and finally there is a section (an appendix) on stock indexes.