Slow transportation and food preservation techniques (based on drying, salting, smoking and pickling) made long-distance trade of many foods very expensive. Because of this, the nobility's food was more prone to foreign influence than the cuisine of the poor; it was dependent on exotic spices and expensive imports. As each level of society imitated the one above it, innovations from international trade and foreign wars from the 12th century onward gradually disseminated through the upper middle class of medieval cities. Aside from economic unavailability of luxuries such as spices, decrees outlawed consumption of certain foods among certain social classes and sumptuary laws limited conspicuous consumption among the nouveaux riches. Social norms also dictated that the food of the working class be less refined, since it was believed there was a natural resemblance between one's labour and one's food; manual labour required coarser, cheaper food.