Barriers to Entry and Market Power

In a competitive market, profit draws in new firms until profit disappears. Barriers to entry are whatever blocks that process. Three common ones: high start-up costs mean a new firm needs so much capital just to build a plant or network that few can risk it; patents give one firm the sole legal right to sell an invention for a fixed period, shutting out copycats entirely; and control of a key resource means one firm owns the only input a product needs, so rivals literally cannot get the materials to compete. Each barrier works differently but ends the same way: the incumbent faces no serious rival, so it keeps the power to set its own price instead of accepting the market price.

That power is called market power, and it shows up as a downward-sloping demand curve facing the firm itself, rather than the flat, price-taking demand a competitive firm sees. The firm chooses a point on that curve, but it cannot choose price and quantity independently. Charge more and buyers walk away; the firm trades sales for margin, it does not escape the tradeoff.

This connects directly to what comes next in the unit: because the monopolist is not a price taker, marginal revenue falls below price at every unit sold, which is what ultimately produces the lower output and deadweight loss studied later. Barriers to entry are the reason that gap between price and marginal cost can persist for years instead of vanishing like it would under competition.