What do economists (and used-car dealers) mean by a "lemon"?

A "lemon" is a term used to describe a product or item, generally a used car, that has undisclosed defects or is of poor quality. This term is often used in the context of the used-car market, where buyers may not have complete information about the vehicle's history and potential issues.

Information asymmetry occurs when one party in a transaction has more or better information than the other party. In the used-car market, sellers may know more about the vehicle's history and condition, while buyers may not have access to all the required information to make an informed decision. This imbalance of information can lead to several problems, such as moral hazard and adverse selection.

Adverse selection is a phenomenon that arises due to information asymmetry when transactions involve the trade of products or services with hidden attributes or characteristics. Adverse selection can lead to a situation called the "lemons problem." In the used-car market, this may occur when low-quality cars ("lemons") drive high-quality cars out of the market. The reasoning is that the buyers cannot differentiate between the good quality and low-quality cars, and thus, they are only willing to pay an average price for all. This average price is too low for sellers with high-quality cars, which forces them to leave the market, leaving only "lemons" behind.

In 1970, economist George Akerlof presented the "Market for Lemons" model, which described the impact of information asymmetry and adverse selection on the used-car market. In his model, Akerlof demonstrated how the market can break down because of the inability to accurately assess the quality of products. As a result, the market's inefficiency causes good quality products to be driven out of the market, leaving only low-quality items, like "lemons," for sale. In conclusion, a "lemon" is a term used to describe a low-quality or defective product, usually in the context of the used-car market. The presence of "lemons" highlights the issues of information asymmetry and adverse selection, leading to market inefficiencies and consumer dissatisfaction.