market is in long-run equilibrium and firms in this market have identical cost structures. Suppose demand in this market decreases. Which of the following will happen to the market quantity as the market leaves and then returns to long-run equilibrium?

There will be oversupply. Pressure will be exerted on price. Weak producers will leave. Supply will fall. Price will rise. A new long run equilibrium will be attained, albeit at a lower equilibrium quantity.

Explanation:

Change in demand or supply will cause the equilibrium position to change. Given a constant supply, a reduced demand would result in supply overshadowing demand. Identical cost structure means that the profit margin would be further reduced which would force weak players in the market to exit the market as well as reduce the incentive to produce more by the remaining players given the poor margin. As the producers exit the market, the market supply falls and price increases. Eventually, equilibrium price returns to its long run equilibrium but at a lower quantity of transaction in the market.