Shifts in the extent of competition, which affect markup ratios, are possible sources of aggregate business fluctuations. markups are countercyclical, and booms are times at which the economy operates more efficiently. We begin with a real model in which markup ratios correspond to the prices of...

Economies at early stages of development are often shaken by abrupt changes in growth rates, whereas in advanced economies growth rates tend to be relatively stable. To explain this pattern, we propose a theory of technological diversification. Production makes use of different input varieties,...