What measures producer surplus?

The measure of producer surplus is defined as the difference between the price that producers actually receive for a good or service and the minimum price they are willing to accept in order to produce that good or service. This concept highlights the benefit that producers get from selling at a market price that exceeds their costs or minimum acceptable price.

When producers are willing to sell at a lower price but are able to sell at a higher market price, the difference represents additional earnings for them. This surplus not only incentivizes producers to supply more of the good but also reflects the benefits they gain from favorable market conditions.

The other options do not accurately describe producer surplus. The total quantity sold pertains more to market dynamics rather than surplus; the cost of production versus market demand does not specifically focus on the difference between price received and willingness to sell; and the reduction in sales prices does not capture the concept of excess earnings above the cost of production. Thus, the correct measure of producer surplus is indeed the difference between what producers receive and their willingness to sell.