This paper proposes a simple method for guiding researchers in developing quantitative models of economic fluctuations. We show that a large class of models, including models with various frictions, are equivalent to a prototype growth model with time varying wedges that, at least on face value, look like time-varying productivity, labor taxes, and capital income taxes. We label the time varying wedges as efficiency wedges, labor wedges, and investment wedges. We use data to measure these wedges and then feed them back into the prototype growth model. We then assess the fraction of fluctuations accounted for by these wedges during the great depressions of the 1930s in the United States, Germany, and Canada. We find that the efficiency and labor wedges in combination account for essentially all of the declines and subsequent recoveries. Investment wedge plays at best a minor role.

We look for the scale effects on growth predicted by some theories of trade and growth based on dynamic returns to scale at the national or industry level. The increasing returns can arise from learning by doing, investment in human capital, research and development, or development of new products. We find some evidence of a relation between growth rates and the measures of scale implied by the learning by doing theory, especially total manufacturing. With respect to human capital, there is some evidence of a relation between growth rates and per capita measures of inputs into the human capital accumulation process, but little evidence of a relation with the scale of inputs. There is also little evidence that growth rates are related to measures of inputs into R&D. We find, however, that growth rates are related to measures of intra-industry trade, particularly when we control for scale of industry.

We study a variant of the one-sector neoclassical growth model of Diamond in which capital investment must be credit financed, and an adverse selection problem appears in loan markets. The result is that the unfettered operation of credit markets leads to a one-dimensional indeterminacy of equilibrium. Many equilibria display economic fluctuations which do not vanish asymptotically; such equilibria are characterized by transitions between a Walrasian regime in which the adverse selection problem does not matter, and a regime of credit rationing in which it does. Moreover, for some configurations of parameters, all equilibria display such transitions for two reasons. One, the banking system imposes ceilings on credit when the economy expands and floors when it contracts because the quality of public information about the applicant pool of potential borrowers is negatively correlated with the demand for credit. Two, depositors believe that returns on bank deposits will be low (or high): these beliefs lead them to transfer savings out of (into) the banking system and into less (more) productive uses. The associated disintermediation (or its opposite) causes banks to contract (expand) credit. The result is a set of equilibrium interest rates on loans that validate depositors' original beliefs. We investigate the existence of perfect foresight equilibria displaying periodic (possibly asymmetric) cycles that consist of m periods of expansion followed by n periods of contraction, and propose an algorithm that detects all such cycles.

This paper proposes a model of diversifiable uncertainty, irreversible investment decisions, and endogenous growth. The detailed microeconomic structure of the model makes it possible to study the. general equilibrium effects of obstacles to labor mobility, due to institutional as well as technological features of the economy. Labor mobility costs reduce private returns to investment, and the resulting slower rate of endogenous growth unambiguously lowers a representative individual's welfare. Turnover costs can have positive effects on full employment equilibrium wages when all external effects are disregarded: this may help explain why policy and institutions often tend to decrease labor mobility in reality, rather than to enhance it. Lower flexibility, however, reduces the growth rate of wages in endogenous growth equilibrium, with negative welfare effects even for agents who own only labor.

This paper examines the determination of the rate of growth in an economy in which two political parties, each representing a different social class, negotiate the magnitude and allocation of taxes. Taxes may increase growth if they finance public services, but reduce growth when used to redistribute income between classes. The different social classes have different preferences about growth and redistribution. The resulting conflict is resolved through the tax negotiations between the political parties. I use the model to obtain empirical predictions and policy lessons about the relationship between economic growth and income inequality. In particular, I show that, although differences in growth rates across countries may be negatively related to income inequality, redistributing wealth does not enhance growth.

The process by which per capita income in the South converged to northern levels is intimately related to the structural transformation of the U.S. economy. We find that empirically most of the southern gains are attributable to the nation-wide convergence of agricultural wages to non-agricultural wages, and the faster rate of transition of the Southern labor force from agricultural to non-agricultural jobs. Similar results describe the Mid-West's catch up to the North-East (but not the relative experience of the West). To explain these observations, we construct a model in which the South (Mid-West) has a comparative advantage in producing unskilled-labor intensive agricultural goods. Thus, it starts with a disproportionate share of the unskilled labor force and lower per capita incomes. Over time, declining education/training costs induce an increasing proportion of the labor force to move out of the (unskilled) agricultural sector and into the (skilled) non-agricultural sector. The decline in the agricultural labor force leads to an increase in relative agricultural wages. Both effects benefit the South (Mid-West) disproportionately since it has more agricultural workers. The model successfully matches the quantitative features of the U.S. structural transformation and regional convergence, as well as several other stylized facts on U.S. economic growth in the last century. The model does not rely on frictions on factor mobility, since in our empirical work we find this channel to be less important than the compositional effects the model emphasizes.

This paper presents a model in which a country's average propensity to save tends to rise endogenously over time. The paper uses a two-sector neoclassical framework to model the transition from agriculture to manufacturing which typically accompanies economic development. Key assumptions are that only the agricultural sector uses land and a simple version of Engel's law. When a country's income per capita is low, agricultural consumption is important; consequently, land is valuable and capital gains on it may account for most wealth accumulation, making the NIPA APS appear low. If exogenous technological progress raises incomes over time, Engel's law shifts demand to manufactured goods. Then land's importance in portfolios relative to reproducible capital diminishes and the measured average propensity to save can rise.

In a world with two similar, developed economies, economic integration can cause a permanent increase in the worldwide rate of growth. Starting from a position of isolations, closer integration can be achieved by increasing trade in goods or by increasing flows of ideas. We consider two models with different specifications of the research and development sector that is the source of growth. Either form of integration can increase the long-run rate of growth if it encourages the worldwide exploitation of increasing returns to scale in the research and development sector.