Musings on a Famous Portfolio Asset Allocation Study

Some Critics Claim Brinson, Hood, and Beebower Conclusions Wrong

[By Dr. David Edward Marcinko MBA CMP™]


Frequently, we hear the axiom that asset allocation is the most important investment decision, explaining 93.6% of portfolio returns. The presumption has been that once the risk tolerance and time horizon have been established, investing is simply a matter of implementing a fixed mix of stocks, bonds, and cash using mutual funds selected for this purpose. This axiom is based on a famous study by Brinson, Hood, and Beebower (BHB) published in the Financial Analysts Journal in July/August 1986. It is the stuff of most modern business school and graduate students in economics and finance.

Enter the Critics

One critic claims that BHB’s conclusions and the interpretation of their conclusions are wrong, stating that because of several methodological problems, BHB needed to make certain assumptions for their analysis to go forward. They assumed that the average asset-class weights for the 10-year period studied are the same as the actual normal policy weights; that investments in foreign stocks, real estate, private placements, and venture capital can be proxied by a mix of stocks, bonds, and cash; and that the benchmarks for stocks, bonds, and cash against which fund performance was measured are appropriate. The author believes that each of these assumptions can lead to a faulty measurement of success or failure at market timing and stock selection.

The Jahnke Study

William Jahnke claims that BHB erred in their focus on explaining the variation of quarterly portfolio returns rather than portfolio returns over the 10-year period studied. According to the study, asset allocation policy explains only a small fraction of the range of 10-year portfolio returns earned by the pension funds reported in the study. The author concluded that this discrepancy is caused by the effect of compounding returns. He adds that BHB were wrong to use variance of quarterly returns rather than the standard deviation. Use of standard deviation would reduce the often cited 93.6% to about 79%. Moreover, BHB did not consider the cost of investing, such as operating expenses, management fees, brokerage commissions, and other trading costs, which are more significant for individual investors than for the pension plans studied. Jahnke claims that excessive costs can reduce wealth accumulation by 50%.

Note: (“The Asset Allocation Hoax,” William W. Jahnke, Journal of Financial Planning, February 1997, Institute of Certified Financial Planners [303] 759-4900).


Finally, the author takes issue with establishing long-term fixed asset class weights. Asset allocation should be a dynamic process. Higher equity return expectations should in turn produce larger equity allocations, other things being equal.

Certified Medical Planner


Are doctors different than the average investor noted in this essay?

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