Does the market share held by the defendant threaten competition? How large that share must be to raise monopoly concerns depends on a variety of considerations, including how fragmented or concentrated the market is. The Harvard Law Review provides some approximate boundaries: Market share above 70 percent typically suffices to support an inference of monopoly power. Conversely, courts have rarely found monopoly power when a firm’s market share is below 50 percent, leaving some uncertainty as to market shares between 50 and 70 percent. Market share alone, however, does not establish monopoly power. Barriers to entry, economies of scale, the strength of the competition, trends in the market, and pricing patterns all help to determine whether the market remains competitive despite a single firm’s large share. 

Question 

Why are the courts interested in barriers to entry?