Apr 24, 2009
Recently, Professor Jeremy Siegel has challenged the method of calculating earnings for the S&P 500. He believes the calculation should be market weighted, as is the index. Standards and Poor's disagrees. In your view, who is correct?

EFF/KRF: In our research we calculate the E/P ratio for a portfolio just as S&P does, dividing the aggregate earnings of the firms in the portfolio by the total market equity. It is easy to see the logic if you imagine merging all of the firms into one giant conglomerate. The new firm's earnings and market equity are just the sum of the individual firms' earnings and market equity.

Eugene F. Fama
The Robert R. McCormick Distinguished Service Professor of Finance at the University of Chicago Booth School of Business
Kenneth R. French
The Roth Family Distinguished Professor of Finance at the Tuck School of Business at Dartmouth College
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Eugene Fama and Ken French are members of the Board of Directors for and provide consulting services to Dimensional Fund Advisors LP.