consider this scenario: buyers of used pianos know the quality of the average used piano, so they are only willing to pay a price for a used piano that is consistent with this average quality. as a result, owners of used pianos of higher-than-average quality leave the market. this reduces average quality and the price buyers are willing to pay, driving more used pianos out of the market. this process continues until only the worst used pianos are left in the market. this process is referred to in the video as: