The responses to Jim's tweet illustrate a problem with the way most economists use the term monopoly, to mean *any* deviation from perfectly competitive general equilibrium. "Monopoly power" in this sense exists in every market (even the wheat markets of intro textbooks). 1/ https://twitter.com/JamesSurowiecki/status/1200438830580543488

By "monopoly" Jim obviously means something like "the absence of meaningful competition," a situation that obviously doesn't apply to big retailers (or Big Tech). Replying "duh, third-degree price discrimination is only possible for firms with monopoly power" misses the point. 2/

Even continuous measures like price-cost markups and HHI etc. don't capture "competition" in a meaningful sense (rivalry, dynamics, entrepreneurship, potential entry, etc.). https://mises.org/library/meaning-competition 3/

The question of whether Amazon etc. face meaningful competition is interesting and important, and the neoclassical notion of perfect competition doesn't help us answer it. Here are some old O&M posts on different aspects of competition. https://organizationsandmarkets.com/?s=Competition+&searchbutton 4/4