Dangers of Using a Company-Wide Discount Rate

Any Finance 101 class will emphasize that the appropriate discount rate for a project depends on the project’s own characteristics, not the firm as a whole. If a utilities firm moves into media (e.g. Vivendi), it should use a media beta - not a utilities beta - to calculate the discount rate . However, a survey found that 58% of firms use a single company-wide discount rate for all projects, rather than a discount rate specific to the project’s characteristics. Indeed, when I was in investment banking, several clients would use their own cost of capital to discount a potential M&A target's cash flows. 

But the important question is – does this really matter? Perhaps an ivory-tower academic will tell you the correct weighted average cost of capital (WACC) is 11.524% but if you use 10%, is that good enough? Given the cash flows of a project are so difficult to estimate to begin with, it seems pointless to “fine-tune” the WACC calculation.

An interesting paper, entitled “The WACC Fallacy: The Real Effects of Using a Unique Discount Rate”, addresses the question. The paper is forthcoming in the Journal of Finance and co-authored by Philipp Krueger of Geneva, Augustin Landier of Toulouse and David Thesmar of HEC Paris. 

This paper shows that it matters. The authors first looked at organic investment (capital expenditure, or "capex"). If your core business is utilities and the non-core division is media, you should be using a media discount rate for non-core capex. But, if you incorrectly use a utilities discount rate, the discount rate is too low and you'll be taking too many projects. The authors indeed find that capex in a non-core division is greater if the non-core division has a higher beta than the core division. Moreover, they find the effect is smaller (a) in recent years, consistent with the increase in finance education (e.g. MBAs), (b) for larger divisions – if the non-core division is large, then management puts the effort into getting it right, (c) when management has high equity incentives, as these also give them incentives to get it right.

The authors then turn to M&A. They find that conglomerates tend to buy high-WACC targets rather than low-WACC targets, again consistent with them erroneously using their own WACC to value a target, when they should be using the target’s own high WACC. Moreover, the attraction of studying M&A is the authors can measure the stock market’s reaction to the deal, to quantify how much value is destroyed. They find that shareholder returns are 0.8% lower when the target’s WACC is higher than the acquirer’s WACC. They study 6,115 deals and the average acquirer size is $2bn. Thus, the value destruction is 0.8% * $2bn * 6,115 = $98bn lost to acquirers in aggregate because they don’t apply a simple principle taught in Finance 101!

We often wonder whether textbook finance theory is relevant in the real world – perhaps you don’t need the “academically” right answer and it's sufficient to be close enough. But this paper shows that “getting it right” does make a big difference.