Final answer:
Some indications of forthcoming collusion include patterns of identical pricing, market division, stable market shares, and limiting production to influence prices. These behaviors point to an implicit understanding among firms to avoid competition, which is hard to prove, making collusion enforcement challenging.
Step-by-step explanation:
Indications that collusion could be forthcoming often involve observable patterns of behavior among firms that suggest a tacit understanding or agreement to not compete aggressively. Such behavioral patterns can include setting identical prices, dividing markets, maintaining market shares over long periods without significant fluctuation, and reducing output or limiting production in a manner that maintains or increases prices without clear cost justification. While formal cartels provide concrete evidence of collusion and are therefore rare in the United States, most collusion is tacit due to the difficulty of enforcement agencies like the Antitrust Division of the Justice Department and the Federal Trade Commission in finding hard evidence of these covert understandings.