In a perfectly competitive market, long-run equilibrium adjustments occur when firms exit due to economic losses, which typically leads to a return of the market price to its original level, assuming costs remain constant. This process highlights that the industry's ___ remains unchanged despite fluctuations in the number of firms.

In a perfectly competitive market, when some firms exit because they are losing money, it actually helps the remaining firms. As these firms leave, there are fewer products available in the market, which can cause the price to rise back to the original level where firms can make a profit. This adjustment shows that the overall industry supply curve remains unchanged in the long run, even if the number of firms changes. For example, if a market for apples sees some farmers go out of business due to low prices, the remaining farmers can increase their prices, allowing them to cover their costs again. Thus, the market can stabilize, demonstrating the resilience of the industry supply in response to shifts in the number of firms.