In an oligopoly, if a firm is earning a positive economic profit, it is guaranteed that new competitors will enter the market immediately, driving the profit to zero.

In an oligopoly, a few companies dominate the market, and if one of them is making a positive economic profit, it means they are earning more than just covering their costs. This profit attracts new competitors because they want to take advantage of the opportunity to earn money too. However, unlike in perfect competition, new firms may not enter the market immediately due to high barriers like expensive equipment or strong brand loyalty. Over time, if the profit continues, some firms may find a way to enter, which can increase competition. Eventually, this competition can drive profits down to zero, as companies will lower their prices to attract customers.