Monopoly

Monopoly begins with a market boundary, not a company name. One seller of a brand is not necessarily the only seller in the relevant market if buyers can switch to products that discipline its terms. Conversely, a market can be narrower than a broad industry label when alternatives do not serve the same buyers, use, location, or time.

A monopolist faces the market demand relationship rather than a horizontal price-taking demand line. That does not mean it can charge any price. Buyer response, willingness and ability to pay, costs, capacity, durable-good resale, entry threats, innovation, contracts, regulation, and buyer power constrain choices.

Structure is not a verdict

Single-seller structure does not by itself prove unlawful conduct. Antitrust questions depend on jurisdiction, current law, defined market, power, conduct, effects, defenses, procedure, and evidence. The Standard Oil history belongs in that institutional analysis; it is not a timeless shortcut from “large firm” to liability.

Accounting revenue, margin, assets, and segment data can inform the record, but do not alone define the market or prove durable market power. A high accounting margin may reflect risk, innovation, intangible investment, measurement, temporary scarcity, differentiation, or power; those explanations must be tested.