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,...

The first wave of globalization (1830-1914) witnessed a decline in the number of countries from 125 to 54. Political consolidation was often achieved through war and conquest. The second wave of globalization (1950-present) has led instead to an increase in the number of countries to a record...