Final answer:
Tacit collusion involves oligopolistic firms informally working together to behave like a monopoly, increasing prices and limiting production without a formal agreement, making it hard to detect and enforce.
Step-by-step explanation:
Tacit collusion in an oligopolistic industry occurs when firms in a market implicitly reach an understanding that competition is bad for profits. Without any explicit agreement or formal collusion like a cartel, these firms tend to act together to hold down industry output, charge higher prices, and divide up the profit among themselves
Behaving akin to a monopoly. This form of collusion is challenging to detect and enforce against because it lacks hard evidence since firms coordinate indirectly, often observing and matching each other's pricing and production levels.