A restless market, and what financial management is for

Many markets, the notes begin, including the United States, which they treat as representative of world capital markets, have faced difficulty. The United States has periodically gone through stretches of confusion in its capital market, and Korea, whose capital market has developed since the 1980s, has also seen market volatility about every four or five years. After countries established strong central banks, they write, the banking systems of advanced countries were not shaken to the roots. Even when financial markets were in confusion, advanced-country banks held the line, and a slump in the real economy could be brought under control. They name, as cases in which banks in the United States or Europe did not collapse, the cascade of U.S. savings-and-loan (S&L) failures in the 1980s, the collapse of the hedge fund Long-Term Capital (LTCM) in the 1990s, and the bursting of the IT bubble in the 2000s.

As part of an effort to keep one’s own assets safe, they write, portfolio theory, the CAPM, and the APT were developed. Financial management, in their account, is the discipline that studies how a firm raises the funds it needs, and how it uses those funds, efficiently, together with the theory and the techniques for doing so. Its main functions are the investment decision, about the kinds and scale of assets to hold; the financing decision, about capital structure; and the dividend decision, about dividing net profit between retained earnings and a dividend.

Portfolio theory, and the CAPM’s market line

Portfolio theory, they write, is mainly a comparison: the relation of expected return and risk when one invests in a single stock, set against the same relation when one invests in a portfolio of several stocks. Among the terms they use, expected utility is the mean of the future probability distribution of the utility an investment will yield; a rational investor, also called a reasonable investor, is risk-averse and aims to maximize expected utility; and a risk premium is expected return minus a certainty equivalent.

The CAPM, or capital asset pricing model, adds a few assumptions to Markowitz’s portfolio theory, finds a linear relation between risk and expected return, and from that works out the equilibrium return of a stock or a portfolio. The present value found by discounting the stock’s expected future cash flows at that return is, they write, the stock’s equilibrium price. A risk-free asset is assumed to exist, and may be borrowed or lent (invested) in any amount at the risk-free rate. Among the many conditions of a perfect market, the important ones they name are that there are no taxes and no transaction costs, and that assets are infinitely divisible. The capital market line (CML) shows a linear relation between the expected return of an efficient portfolio and its risk (the standard deviation); the portfolio with the steepest slope becomes, in the end, the only efficient portfolio, and is called the market portfolio. The security market line (SML) shows the relation of expected return and risk for every investment asset, including inefficient ones.

Ross’s APT of 1976, and why they call it more general

The APT, or arbitrage pricing theory, is, they write, a pricing model Ross derived from a factor model in 1976. Among its assumptions they note a perfect market, with no transaction costs, no taxes, and no other frictions of trade. A shared assumption with portfolio theory is that investors are risk-averse and wish to maximize expected utility. The decisive difference, as they draw it, is this: the CAPM tries to explain expected return with beta alone, and lets the expected return of an individual stock be affected only by one common factor, the market portfolio — a single-factor model. The APT starts from the assumption that several factors determine return, and is derived from a multi-factor model, so it is a more generalized equilibrium model, and the CAPM may be seen as a special case of the APT.

The CAPM also assumes, they add, that investors act on a mean-variance criterion, and therefore that the probability distribution of returns is normal, or that the investor’s utility function has a quadratic form. The APT does not need those assumptions; it needs only the assumption that if an opportunity for arbitrage exists, investors will seek an arbitrage profit. For that reason too, they write, the APT is the more general model. Those contrasts, and the market episodes they name, are left in the notes’ own window. The same Korean report, at fuller length, is on CampusDown.

Sources

1. The notes’ account of portfolio theory, the CAPM, and Ross’s APT of 1976, including the differences they draw between the two models

Last updated: 14 November 2026