During research for his marketing course, Chandler found that although traditional marketers don't pay much attention to used-product sellers, factors such as concern about the environment, demands for quality, cost, and fashion consciousness make these secondary markets more important. In fact, economic estimates of the ______________ range from 3 to 30 percent of the gross national product of the United States and up to 70 percent of the gross domestic product of other countries.
Answer: underground economy