One approach to urban areas emphasizes the existence of certain immutable relationships, such as Zipf's or Gibrat's Law. An alternative view is that urban change reflects individual responses to changing tastes or technologies. This paper examines almost 200 years of regional change in the U.S....

After decades of successful growth, economic unions have recently become the focus of heightened political controversy. We argue that this is partly due to the growth of trade between countries that are increasingly dissimilar. We develop a theoretical framework to study the effects on trade,...