Market-definition economist
Expert class library · Antitrust · Either side
Defines the relevant product and geographic market in which the defendant's conduct should be judged and measures market power within it. That market definition is the foundation for monopolization, tying, merger, and rule-of-reason claims, so courts scrutinize whether it rests on real substitution evidence.
What this expert is retained to answer
- Would a hypothetical monopolist of the proposed product set profitably impose a small but significant and non-transitory price increase?
- Does the aggregate diversion ratio exceed the critical loss threshold for the candidate market?
- Can the market properly be drawn around a group of targeted customers who would not switch in response to a price increase?
- Which firms belong in the market, and what are their shares and the resulting concentration?
- Does the market definition fit the theory of harm, such as the tying or tied product market?
Methods
- Hypothetical monopolist (SSNIP) test
- Critical loss analysis
- Diversion ratio estimation
- Concentration measures (HHI)
How the testimony is attacked
- Market narrowed without substitution evidence. Opponents argue the expert carved out a submarket without showing customers would refuse to substitute. In It's My Party v. Live Nation the court excluded the venue market definition because the data on artist preference for amphitheaters did not show artists would stay put if prices rose.
- Data that does not measure price response. Defendants argue that win-loss or customer relationship data cannot show how buyers react to price changes. The Ninth Circuit in Teradata v. SAP held that the hypothetical monopolist test asks about likely diversion, so such data can reliably support an aggregate diversion ratio.
- Misapplied critical loss analysis. Challengers say the expert should have calculated actual loss or used a different margin measure. In Dial Corp. v. News Corp. the court treated disputes over the critical loss inputs and the Lerner index as matters of weight for the jury.
- Inconsistent market boundaries across the analysis. Defendants attack an expert who uses different sets of market participants for the tying and tied markets. The Ninth Circuit held that tailoring the participant set to the theory of harm was grounded in economic logic and satisfied Rule 702.
- Market defined to suit the plaintiff's case. Opponents argue the boundaries were chosen to inflate shares, for example by excluding nearby reasonable substitutes. The Live Nation court found the market suited the plaintiffs' needs while omitting potential substitute venues in the vicinity.
What the public record shows
A deliberately narrow CourtListener search, "hypothetical monopolist" AND "relevant market" AND (Daubert OR "Rule 702"), returned 4 opinions filed since 2015, as of October 2, 2026; broader searches return more. Three that show how courts handle this class of testimony:
| Outcome | Case | Court | Why |
|---|---|---|---|
| Excluded | It's My Party, Inc. v. Live Nation, Inc.88 F. Supp. 3d 475 | D. Md. 2015 | The court excluded the plaintiffs' expert's venue market definition because the histogram and anecdotal evidence of artists preferring amphitheaters lacked sufficient facts and did not show those artists would refuse to switch venues if prices rose. |
| Admitted | Dial Corp. v. News Corp.165 F. Supp. 3d 25 | S.D.N.Y. 2016 | The court denied the motion to exclude the plaintiffs' economist, holding that disputes over his SSNIP and critical loss analysis, benchmark margins, and use of the Lerner index went to weight rather than admissibility. |
| Exclusion reversed | Teradata Corp. v. SAP SE124 F.4th 555 | 9th Cir. 2024 | The Ninth Circuit held the district court abused its discretion in excluding the plaintiff's tied-market definition, because an aggregate diversion ratio built from customer relationship data is an accepted way to implement the hypothetical monopolist test. |
Each case links to the free opinion text on CourtListener.
Under amended Rule 702
Since December 1, 2023, Rule 702 says expressly that the party offering an expert must show the court it is more likely than not that the testimony meets each requirement: that it rests on sufficient facts or data, uses reliable methods, and reflects a reliable application of those methods to the case. Questions about the basis of an opinion are no longer automatically matters of weight for the jury. For how the circuits have applied the amendment, see the Rule 702 tracker, which follows each court of appeals; for what that means for preparing or attacking this class of expert, see the guide on amended Rule 702.
Related classes
Guides
- Common Impact and Pass-Through at Class Certification
- Amended Rule 702 After Nearly Three Years: What Courts Exclude
Simulating this class on a matter
Supreme Mind simulates a class of expert, never a named individual, on your fact pattern and returns the likely opinion, the ranked cross-examination weaknesses, the Rule 702 attack surface and what it means for settlement. Read how it works, or book a demo.
Last reviewed October 2, 2026. How this page is built: rulings are found by searching court opinions on CourtListener, and each one is read in the opinion before it is summarised here; outcomes are labelled by what the court did with the expert's testimony. No individual expert is named. This page summarises public decisions for orientation and is not legal advice; read the opinion before relying on any ruling.