Portfolio Constraints and the Fundamental Law of Active Management

Posted: 14 Nov 2001

See all articles by Steven Thorley

Steven Thorley

BYU Marriott School of Business

Roger Clarke

affiliation not provided to SSRN

Harindra de Silva

Analytic Investors, Inc.

Multiple version iconThere are 2 versions of this paper


Active portfolio management is typically conducted within constraints that do not allow managers to fully exploit their ability to forecast returns. Constraints on short positions and turnover, for example, are fairly common and materially restrictive. Other constraints, such as market-capitalization and value-growth neutrality with respect to the benchmark or economic-sector constraints, can further restrict an active portfolio's composition. We derive ex ante and ex post correlation relationships that facilitate the performance analysis of constrained portfolios. The ex ante relationship is a generalized version of a previously developed "fundamental law of active management" and provides an important strategic perspective on the potential for active management to add value. The ex post correlation relationship represents a practical decomposition of performance into the success of the return-prediction process and the "noise" associated with portfolio constraints. We verify the accuracy of these relationships with a Monte Carlo simulation and illustrate their application with equity portfolio examples based on the S&P 500 Index as the benchmark.

Keywords: Portfolio Management: portfolio construction, rebalancing, and implementation, Portfolio Management: investment policy

JEL Classification: G11

Suggested Citation

Thorley, Steven and Clarke, Roger and de Silva, Harindra, Portfolio Constraints and the Fundamental Law of Active Management. Available at SSRN: https://ssrn.com/abstract=290322

Steven Thorley (Contact Author)

BYU Marriott School of Business ( email )

616 TNRB
Brigham Young University
Provo, UT 84602
United States
801-378-6065 (Phone)
801-378-5984 (Fax)

Roger Clarke

affiliation not provided to SSRN

Harindra De Silva

Analytic Investors, Inc. ( email )

555 West 5th Street
50th Floor
Los Angeles, CA 90013
United States
213-688-3015 (Phone)
213-688-8856 (Fax)

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