In agrarian societies, some of the simple correlations between social complexity and environment begin to disappear. One view is that humans with this technology have moved a large step toward controlling their environments, are less dependent on them, and hence show fewer correlations between environment and technology-related traits. A rather different view is that as societies become larger and the movement of goods and people cheaper, they incorporate an increasing range of environmental variation within their borders and trade system. But environmental factors may still play a strong role as variables that affect the internal structure and history of a society in complex ways. For example, the average size of agrarian states will depend on the ease of transportation, major cities will tend to be located at trade nodes, and the demographic history of a society may depend on disease episodes.