We introduce, into a version of the Real Business Cycle model, mild increasing returns-to-scale. These increasing returns-to-scale occur as a consequence of sector specific externalities, that is externalities where the output of the consumption and investment sectors have external effects on the output of firms within their own sector. Keeping the production technologies for both sectors identical for expositional simplicity, we show that indeterminacy can easily occur for parameter values typically used in the real business cycle literature, and in contrast to some earlier literature on indeterminacies, for externalities mild enough so that labor demand curves are downward sloping.

There were three important changes in the United States economy during the 1980s. First, from 1982-90, the decade featured the longest consecutive stretch of positive quarterly output growth in United States history. Second, wage inequality expanded greatly as the wages of highly skilled workers grew markedly faster than the wages of less skilled workers (Katz and Murphy (1992)). Finally, consumption inequality also expanded as the consumption of highly skilled workers grew faster than that of less skilled workers (Attanasio and Davis (1994)). This paper argues that these three aspects of the United States economic experience can be interpreted as being part of an efficient response to a macroeconomic shock given the existence of a particular technological impediment to full insurance. I examine the properties of efficient allocations of risk in an economic environment in which the outside enforcement of risksharing arrangements is infinitely costly. In these allocations, relative productivity movements have effects on both the current and future distribution of consumption across individuals. If preferences over consumption and leisure are nonhomothetic, these changes in the allocation of consumption will generate persistent cycles in aggregate output that do not occur in efficient allocations when enforcement is costless.