About the limited social-utility and economic non-productivity of the business social-class, the American business entrepreneur Warren Buffett said that non-productive financial activities, such as day trading (speculative buying-and-selling of financial securities) and arbitrage (manipulation of price-differentials among markets) have vindicated "The Theory of the Leisure Class: An Economic Study of Institutions" (1899), because such activities only produce capital, but do not produce useful goods and services for people.