Studies relating accounting and price data often use the COMPUSTAT or related PDE data base as the source for the accounting data. This practice may introduce a look-ahead bias and an ex-post-selection bias into the study. We examine this problem by comparing results from the standard COMPUSTAT data base with those from a data base which suffers from neither bias. We find that rates of return from portfolios chosen on the basis of accounting data from the two data bases differ significantly. Further, we find that these differences imply different conclusions when we test a specific hypothesis relating accounting and price data. Finally, we propose a number of remedies which may reduce the bias when the standard COMPUSTAT data base is used.

Studies relating accounting and price data often use the COMPUSTAT or related PDE data base as the source for the accounting data. This practice may introduce a look‐ahead bias and an ex‐post‐selection bias into the study. We examine this problem by comparing results from the standard COMPUSTAT data base with those from a data base which suffers from neither bias. We find that rates of return from portfolios chosen on the basis of accounting data from the two data bases differ significantly. Further, we find that these differences imply different conclusions when we test a specific hypothesis relating accounting and price data. Finally, we propose a number of remedies which may reduce the bias when the standard COMPUSTAT data base is used.

William Sharpe's influential Portfolio Theory and Capital Management is as relevant today as when it was first published in 1970. McGraw-Hill is proud to reintroduce tiffs hard-to-Find classic in its original edition. Dr. Sharpe's groundbreaking approach to the Capital Asset Pricing Model (CAPM) laid tile foundation for today's most important investment tools and theories, gave the investment world the stillvital Sharpe Ratio -- and made him the co-recipient of the 1990 Nobel Prize in Economics!A new foreword helps place Dr. Sharpe's synthesis of portfolio and capital markets theories into today's financial environment, while his rules for the intelligent selection of investments tinder conditions of risk remain as fresh today as in 1970. Serious investors and students of finance will respect its history ... as they reabsorb its timeless lessons.

Knowledge of the one‐month interest rate is useful in forecasting the sign as well as the variance of the excess return on stocks. The services of a portfolio manager who makes use of the forecasting model to shift funds between bills and stocks would be worth an annual management fee of 2% of the value of the assets managed. During 1954:4 to 1986:12, the variance of monthly returns on the managed portfolio was about 60% of the variance of the returns on the value weighted index, whereas the average return was two basis points higher.

Knowledge of the one-month interest rate is useful in forecasting the sign as well as the variance of the excess return on stocks. The services of a portfolio manager who makes use of the forecasting model to shift funds between bills and stocks would be worth an annual management fee of 2% of the value of the assets managed. During 1954:4 to 1986:12, the variance of monthly returns on the managed portfolio was about 60% of the variance of the returns on the value weighted index, whereas the average return was two basis points higher.