CAPM não funciona

Determining the right price for a business on the auction block can often befuddle even the most experienced valuation professionals.

For decades, the Capital Asset Pricing Model (CAPM) has been used by business school professors, CFOs, and valuation experts to gain valuable information on risk and price. Unfortunately, the method, which predicts the expected return of an asset as a function of its beta, is not always accurate.

While the CAPM’s limits are widely known, new research shows the extent to which using the method can cause significant errors in the valuation of a company that’s up for sale.

By examining 12,000 takeover bids for private companies between 1977 and 2015, the authors of a forthcoming study show that using the CAPM to value targets leads to valuation errors that correspond to an average range of 12% to 33% of deal values.

The researchers arrived at their results by developing a model that assessed the cumulative abnormal return of the bidder’s stock in response to the bid; the value of the target’s equity as assessed by the market; and the price paid by the bidder.

“The CAPM formula doesn’t work — it doesn’t give the right price of risk,” saidDavid Thesmar,one of the study’s authors and an MIT Sloan professor of financial economics. “It becomes a problem to actually evaluate businesses when we want to buy them, because we don’t know the price of risk, and we’re using that formula.”

Experts have used the CAPM for years, especially in business schools when introducing ideas of risk and return, portfolio theory, diversification, and other fundamental concepts. The authors estimated in their research that between 73.5% and 90% of CFOs and valuation professionals still use the CAPM.

Dessaint, Olivier and Olivier, Jacques and Otto, Clemens A. and Thesmar, David, CAPM-Based Company (Mis)valuations (October 24, 2019). Rotman School of Management Working Paper No. 3050928.