(Time) - The international wine market was a favorite subject for classical economists in the 18th and 19th centuries to help explain the benefits of free trade. Adam Smith advocated free trade in his opus, An Inquiry into the Nature and Causes of the Wealth of Nations. He wrote against the backdrop of mercantilism, which urged countries to export products to accumulate gold and import as little as possible so that they could husband their yellow metal. Smith mused that he might be able to make wine in his native Scotland. “By means of glasses, hotbeds and hot walls, very good grapes can be raised in Scotland, and very good wine, too, can be made of them at about 30 times the expense for which at least equally good wine can be bought from foreign countries,” he wrote.