Liner shipping is the business of offering common carrier ocean shipping services in international trade. Since it became an important industry in the 1870s, it has been characterized by various agreements between firms. Historically, since the formation in 1875 of the Calcutta Conference, the conference system was the primary form of agreement in liner shipping. Variously called liner conferences, shipping conferences, and ocean shipping conferences, they are formal agreements between liner shipping lines on a route, always setting (possibly discriminatory) prices, and sometimes pooling profits or revenues, managing capacity, allocating routes, and offering loyalty discounts. Conferences agreements were quite successful and in many cases have lasted for years. In the last two decades, conferences have begun to be supplanted by alliances (particularly in the American and European trades, where legislative changes have been unfavourable to them), which are less complete (they do not, for example, set prices) but encompass more broadly defined trade routes.