Portfolio Theory: As I Still See It

This essay summarizes my views on (a) the foundations of portfolio theory and its applications to current issues, such as the choice of criteria for practical risk-return analysis, and whether some form of risk-return analysis should be used in fact; (b) hypotheses about actual financial behavior, as opposed to idealized rational behavior, including two proofs of the fact that expected-utility maximizers would never prefer a multiple-prize lottery to all single-prize lotteries, as asserted in one of my 1952 papers; and (c) a simple proof of the theorem (which was initially greeted with some skepticism, especially by referees) that investors in capital asset pricing models do not get paid for bearing risk.