Final answer:
In the United States, a pharmaceutical company's patent typically lasts for 20 years, providing enough time for the company to make a return on investment yet preventing permanent monopoly pricing.
Step-by-step explanation:
In the United States, a pharmaceutical company's exclusive patent rights last for 20 years. This time frame is designed to balance the need for innovators to earn a good return on their investment and the need to prevent them from holding a monopoly on their invention indefinitely. Patents allow the company that holds them to earn monopoly profits by being the sole manufacturer and seller of a drug they developed, which provides a strong incentive for continuous research and development. After the expiration of the 20-year period, other companies may manufacture generic versions of the patented drug, thereby increasing competition and potentially lowering prices for consumers.