DoorDash, Inc. (DASH)

Marketplace economics come down to route arithmetic: if a courier carries one order the delivery loses money; if a second and third are picked up along the way it earns. The company therefore grows by density inside markets already entered rather than by entering new ones, and its results differ sharply between cities.

The second, higher-margin source is advertising: restaurants pay for placement in the app where the user has already arrived intending to order. That revenue carries almost no variable cost and grows faster than delivery.

Expansion goes beyond food — groceries, pharmacy, retail goods — which raises order frequency from the same user. Risks: courier classification, regulation of the commissions charged to restaurants, and competition with Uber. The company pays no dividend.