If a small number of firms have a large combined market share in a properly defined market, it is strong evidence that those firms have substantial market power.
Responses
Responses weighted by each expert's confidence
| Participant | University | Vote | Confidence | Bio/Vote History |
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 Daron Acemoglu |
MIT | Bio/Vote History | ||
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Yes of course, modern IO has warned us against this. But if it looks, walks and quacks like a duck, it is most probably a duck.
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 Alberto Alesina |
Harvard | Bio/Vote History | ||
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 Joseph Altonji |
Yale | Bio/Vote History | ||
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 Alan Auerbach |
Berkeley | Bio/Vote History | ||
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 David Autor |
MIT | Bio/Vote History | ||
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It is a strong prima facie case, but it is not proof of that case, nor does it mean that they are necessarily exercising that power!
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 Katherine Baicker |
University of Chicago | Bio/Vote History | ||
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 Abhijit Banerjee |
MIT | Bio/Vote History | ||
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 Marianne Bertrand |
Chicago | Bio/Vote History | ||
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 Markus Brunnermeier |
Princeton | Bio/Vote History | ||
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Depends on the nature of competition. Bertrand competition can be more fierce than Cournot competition in this case.
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 Raj Chetty |
Harvard | Did Not Answer | Bio/Vote History | |
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 Judith Chevalier |
Yale | Bio/Vote History | ||
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The number of firms is both an outcome of market competitiveness and an driver of market competitiveness.
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 David Cutler |
Harvard | Bio/Vote History | ||
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 Angus Deaton |
Princeton | Did Not Answer | Bio/Vote History | |
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 Darrell Duffie |
Stanford | Bio/Vote History | ||
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Even with two vendors, market power depends on customer switching costs and delays.
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 Aaron Edlin |
Berkeley | Did Not Answer | Bio/Vote History | |
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 Barry Eichengreen |
Berkeley | Bio/Vote History | ||
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Agree at a very low level of confidence owing to the difficulty of properly defining a market.
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 Liran Einav |
Stanford | Bio/Vote History | ||
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 Ray Fair |
Yale | Bio/Vote History | ||
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 Amy Finkelstein |
MIT | Did Not Answer | Bio/Vote History | |
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 Pinelopi Goldberg |
Yale | Bio/Vote History | ||
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 Austan Goolsbee |
Chicago | Bio/Vote History | ||
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It’s not a guarantee but it’s certainly a risky indicator
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 Michael Greenstone |
University of Chicago | Bio/Vote History | ||
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 Robert Hall |
Stanford | Bio/Vote History | ||
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There is little empirical support for a strong relation--rather, it's a weaker relation.
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 Oliver Hart |
Harvard | Bio/Vote History | ||
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 Bengt Holmström |
MIT | Bio/Vote History | ||
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 Caroline Hoxby |
Stanford | Did Not Answer | Bio/Vote History | |
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 Hilary Hoynes |
Berkeley | Bio/Vote History | ||
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 Kenneth Judd |
Stanford | Bio/Vote History | ||
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They may have market power if they use strategies that implement tacit collusion, but other equilibria do not display market power.
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 Steven Kaplan |
Chicago Booth | Bio/Vote History | ||
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 Anil Kashyap |
Chicago Booth | Bio/Vote History | ||
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 Pete Klenow |
Stanford | Bio/Vote History | ||
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Too many exceptions to be a rule.
-see background information here |
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 Jonathan Levin |
Stanford | Bio/Vote History | ||
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 Eric Maskin |
Harvard | Bio/Vote History | ||
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If a firm has a large market share, then the demand curve it faces is likely to be down-sloping.
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 William Nordhaus |
Yale | Did Not Answer | Bio/Vote History | |
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 Emmanuel Saez |
Berkeley | Bio/Vote History | ||
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 Larry Samuelson |
Yale | Bio/Vote History | ||
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"Large combined market share" is a crude and elusive measure, and is not definitive, but it provides does provide strong evidence.
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 José Scheinkman |
Columbia University | Did Not Answer | Bio/Vote History | |
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 Richard Schmalensee |
MIT | Bio/Vote History | ||
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"Strong" & "substantial" over-state, & "properly-defined" is critical. There is generally market power in markets dominated by a few firms.
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 Carl Shapiro |
Berkeley | Did Not Answer | Bio/Vote History | |
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 Robert Shimer |
University of Chicago | Bio/Vote History | ||
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 James Stock |
Harvard | Bio/Vote History | ||
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 Richard Thaler |
Chicago Booth | Bio/Vote History | ||
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Always one stray word. “Strong”?
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 Christopher Udry |
Northwestern | Did Not Answer | Bio/Vote History | |
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