Leave a Little GUPPI Alone: Why Commissioner Wright is Right to Call for a Low-GUPPI Safe Harbor

Thom Lambert —  14 July 2015

FTC Commissioner Josh Wright has some wise thoughts on how to handle a small GUPPI. I don’t mean the fish. Dissenting in part in the Commission’s disposition of the Family Dollar/Dollar Tree merger, Commissioner Wright calls for creating a safe harbor for mergers where the competitive concern is unilateral effects and the merger generates a low score on the “Gross Upward Pricing Pressure Index,” or “GUPPI.”

Before explaining why Wright is right on this one, some quick background on the GUPPI. In 2010, the DOJ and FTC revised their Horizontal Merger Guidelines to reflect better the actual practices the agencies follow in conducting pre-merger investigations. Perhaps the most notable new emphasis in the revised guidelines was a move away from market definition, the traditional starting point for merger analysis, and toward consideration of potentially adverse “unilateral” effects—i.e., anticompetitive harms that, unlike collusion or even non-collusive oligopolistic pricing, need not involve participation of any non-merging firms in the market. The primary unilateral effect emphasized by the new guidelines is that the merger may put “upward pricing pressure” on brand-differentiated but otherwise similar products sold by the merging firms. The guidelines maintain that when upward pricing pressure seems significant, it may be unnecessary to define the relevant market before concluding that an anticompetitive effect is likely.

The logic of upward pricing pressure is straightforward. Suppose five firms sell competing products (Products A-E) that, while largely substitutable, are differentiated by brand. Given the brand differentiation, some of the products are closer substitutes than others. If the closest substitute to Product A is Product B and vice-versa, then a merger between Producer A and Producer B may result in higher prices even if the remaining producers (C, D, and E) neither raise their prices nor reduce their output. The merged firm will know that if it raises the price of Product A, most of the lost sales will be diverted to Product B, which that firm also produces. Similarly, sales diverted from Product B will largely flow to Product A. Thus, the merged company, seeking to maximize its profits, may face pressure to raise the prices of Products A and/or B.

The GUPPI seeks to assess the likelihood, absent countervailing efficiencies, that the merged firm (e.g., Producer A combined with Producer B) would raise the price of one of its competing products (e.g., Product A), causing some of the lost sales on that product to be diverted to its substitute (e.g., Product B). The GUPPI on Product A would thus consist of:

The Value of Sales Diverted to Product B
Foregone Revenues on Lost Product A Sales.

The value of sales diverted to Product B, the numerator, is equal to the number of units diverted from Product A to Product B times the profit margin (price minus marginal cost) on Product B. The foregone revenues on lost Product A sales, the denominator, is equal to the number of lost Product A sales times the price of Product A. Thus, the fraction set forth above is equal to:

Number of A Sales Diverted to B * Unit Margin on B
Number of A Sales Lost * Price of A.

The Guidelines do not specify how high the GUPPI for a particular product must be before competitive concerns are raised, but they do suggest that at some point, the GUPPI is so small that adverse unilateral effects are unlikely. (“If the value of diverted sales is proportionately small, significant unilateral price effects are unlikely.”) Consistent with this observation, DOJ’s Antitrust Division has concluded that a GUPPI of less than 5% will not give rise to a merger challenge.

Commissioner Wright has split with his fellow commissioners over whether the FTC should similarly adopt a safe harbor for horizontal mergers where the adverse competitive concern is unilateral effects and the GUPPIs are less than 5%. Of the 330 markets in which the Commission is requiring divestiture of stores, 27 involve GUPPIs of less than 5%. Commissioner Wright’s position is that the combinations in those markets should be deemed to fall within a safe harbor. At the very least, he says, there should be some safe harbor for very small GUPPIs, even if it kicks in somewhere below the 5% level. The Commission has taken the position that there should be no safe harbor for mergers where the competitive concern is unilateral effects, no matter how low the GUPPI. Instead, the Commission majority says, GUPPI is just a starting point; once the GUPPIs are calculated, each market should be assessed in light of qualitative factors, and a gestalt-like, “all things considered” determination should be made.

The Commission majority purports to have taken this approach in the Family Dollar/Dollar Tree case. It claims that having used GUPPI to identify some markets that were presumptively troubling (markets where GUPPIs were above a certain level) and others that were presumptively not troubling (low-GUPPI markets), it went back and considered qualitative evidence for each, allowing the presumption to be rebutted where appropriate. As Commissioner Wright observes, though, the actual outcome of this purported process is curious: almost none of the “presumptively anticompetitive” markets were cleared based on qualitative evidence, whereas 27 of the “presumptively competitive” markets were slated for a divestiture despite the low GUPPI. In practice, the Commission seems to be using high GUPPIs to condemn unilateral effects mergers, while not allowing low GUPPIs to acquit them. Wright, by contrast, contends that a low-enough GUPPI should be sufficient to acquit a merger where the only plausible competitive concern is adverse unilateral effects.

He’s right on this, for at least five reasons.

  1. Virtually every merger involves a positive GUPPI. As long as any sales would be diverted from one merging firm to the other and the firms are pricing above cost (so that there is some profit margin on their products), a merger will involve a positive GUPPI. (Recall that the numerator in the GUPPI is “number of diverted sales * profit margin on the product to which sales are diverted.”) If qualitative evidence must be considered and a gestalt-like decision made in even low-GUPPI cases, then that’s the approach that will always be taken and GUPPI data will be essentially irrelevant.
  2. Calculating GUPPIs is hard. Figuring the GUPPI requires the agencies to make some difficult determinations. Calculating the “diversion ratio” (the percentage of lost A sales that are diverted to B when the price of A is raised) requires determinations of A’s “own-price elasticity of demand” as well as the “cross-price elasticity of demand” between A and B. Calculating the profit margin on B requires determining B’s marginal cost. Assessing elasticity of demand and marginal cost is notoriously difficult. This difficulty matters here for a couple of reasons:
    • First, why go through the difficult task of calculating GUPPIs if they won’t simplify the process of evaluating a merger? Under the Commission’s purported approach, once GUPPI is calculated, enforcers still have to consider all the other evidence and make an “all things considered” judgment. A better approach would be to cut off the additional analysis if the GUPPI is sufficiently small.
    • Second, given the difficulty of assessing marginal cost (which is necessary to determine the profit margin on the product to which sales are diverted), enforcers are likely to use a proxy, and the most commonly used proxy for marginal cost is average variable cost (i.e., the total non-fixed costs of producing the products at issue divided by the number of units produced). Average variable cost, though, tends to be smaller than marginal cost over the relevant range of output, which will cause the profit margin (price – “marginal” cost) on the product to which sales are diverted to appear higher than it actually is. And that will tend to overstate the GUPPI. Thus, at some point, a positive but low GUPPI should be deemed insignificant.
  3. The GUPPI is biased toward an indication of anticompetitive effect. GUPPI attempts to assess gross upward pricing pressure. It takes no account of factors that tend to prevent prices from rising. In particular, it ignores entry and repositioning by other product-differentiated firms, factors that constrain the merged firm’s ability to raise prices. It also ignores merger-induced efficiencies, which tend to put downward pressure on the merged firm’s prices. (Granted, the merger guidelines call for these factors to be considered eventually, but the factors are generally subject to higher proof standards. Efficiencies, in particular, are pretty difficulty to establish under the guidelines.) The upshot is that the GUPPI is inherently biased toward an indication of anticompetitive harm. A safe harbor for mergers involving low GUPPIs would help counter-balance this built-in bias.
  4. Divergence from DOJ’s approach will create an arbitrary result. The FTC and DOJ’s Antitrust Division share responsibility for assessing proposed mergers. Having the two enforcement agencies use different standards in their evaluations injects a measure of arbitrariness into the law. In the interest of consistency, predictability, and other basic rule of law values, the agencies should get on the same page. (And, for reasons set forth above, DOJ’s is the better one.)
  5. A safe harbor is consistent with the Supreme Court’s decision-theoretic antitrust jurisprudence. In recent years, the Supreme Court has generally crafted antitrust rules to optimize the costs of errors and of making liability judgments (or, put differently, to “minimize the sum of error and decision costs”). On a number of occasions, the Court has explicitly observed that it is better to adopt a rule that will allow the occasional false acquittal if doing so will prevent greater costs from false convictions and administration. The Brooke Group rule that there can be no predatory pricing liability absent below-cost pricing, for example, is expressly not premised on the belief that low, but above-cost, pricing can never be anticompetitive; rather, the rule is justified on the ground that the false negatives it allows are less costly than the false positives and administrative difficulties a more “theoretically perfect” rule would generate. Indeed, the Supreme Court’s antitrust jurisprudence seems to have wholeheartedly endorsed Voltaire’s prudent aphorism, “The perfect is the enemy of the good.” It is thus no answer for the Commission to observe that adverse unilateral effects can sometimes occur when a combination involves a low (<5%) GUPPI. Low but above-cost pricing can sometimes be anticompetitive, but Brooke Group’s safe harbor is sensible and representative of the approach the Supreme Court thinks antitrust should take. The FTC should get on board.

One final point. It is important to note that Commissioner Wright is not saying—and would be wrong to say—that a high GUPPI should be sufficient to condemn a merger. The GUPPI has never been empirically verified as a means of identifying anticompetitive mergers. As Dennis Carlton observed, “[T]he use of UPP as a merger screen is untested; to my knowledge, there has been no empirical analysis that has been performed to validate its predictive value in assessing the competitive effects of mergers.” Dennis W. Carlton, Revising the Horizontal Merger Guidelines, 10 J. Competition L. & Econ. 1, 24 (2010). This dearth of empirical evidence seems especially problematic in light of the enforcement agencies’ spotty track record in predicting the effects of mergers. Craig Peters, for example, found that the agencies’ merger simulations produced wildly inaccurate predictions about the price effects of airline mergers. See Craig Peters, Evaluating the Performance of Merger Simulation: Evidence from the U.S. Airline Industry, 49 J.L. & Econ. 627 (2006). Professor Carlton thus warns (Carlton, supra, at 32):

UPP is effectively a simplified version of merger simulation. As such, Peters’s findings tell a cautionary tale—more such studies should be conducted before one treats UPP, or any other potential merger review method, as a consistently reliable methodology by which to identify anticompetitive mergers.

The Commission majority claims to agree that a high GUPPI alone should be insufficient to condemn a merger. But the actual outcome of the analysis in the case at hand—i.e., finding almost all combinations involving high GUPPIs to be anticompetitive, while deeming the procompetitive presumption to be rebutted in 27 low-GUPPI cases—suggests that the Commission is really allowing high GUPPIs to “prove” that anticompetitive harm is likely.

The point of dispute between Wright and the other commissioners, though, is about how to handle low GUPPIs. On that question, the Commission should either join the DOJ in recognizing a safe harbor for low-GUPPI mergers or play it straight with the public and delete the Horizontal Merger Guidelines’ observation that “[i]f the value of diverted sales is proportionately small, significant unilateral price effects are unlikely.” The better approach would be to affirm the Guidelines and recognize a safe harbor.

Thom Lambert


I am a law professor at the University of Missouri Law School. I teach antitrust law, business organizations, and contracts. My scholarship focuses on regulatory theory, with a particular emphasis on antitrust.

Trackbacks and Pingbacks:

  1. Leave a Little GUPPI Alone: Why Commissioner Wright is Right to Call for a Low-GUPPI Safe HarborRich Sexton For Congress | RichSextonForCongress - July 15, 2015

    […] Leave a Little GUPPI Alone: Why Commissioner Wright is Right to Call for a Low-GUPPI Safe Harbor […]