Wilbur John Coleman

The U.S. Structural Transformation and Regional Convergence: A Reinterpretation

We present a joint study of the U.S. structural transformation (the decline of agriculture as the dominating sector) and regional convergence (of southern to northern average wages). We find empirically that most of the regional convergence is attributable to the structural transformation: the nationwide convergence of agricultural wages to nonagricultural wages and the faster rate of transition of the southern labor force from agricultural to nonagricultural jobs. Similar results describe the Midwest’s catch‐up to the Northeast (but not the relative experience of the West). To explain these observations, we construct a model in which the South (Midwest) 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) nonagricultural sector. The decline in the agricultural labor force leads to an increase in relative agricultural wages. Both effects benefit the South (Midwest) disproportionately since it has more agricultural workers. With the addition of a less than unit income elasticity of demand for farm goods and faster technological progress in farming than outside of farming, this 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 interregional labor and capital mobility, since in our empirical work we find this channel to be less important than the compositional effects the model emphasizes.

ON THE THEORY OF ETHNIC CONFLICT

We present a theory of ethnic conflict in which coalitions formed along ethnic lines compete for the economy’s resources. The role of ethnicity is to enforce coalition membership: in ethnically homogeneous societies members of the losing coalition can defect to the winners at low cost, and this rules out conflict as an equilibrium outcome. We derive a number of implications of the model relating social, political, and economic indicators such as the incidence of conflict, the distance among ethnic groups, group sizes, income inequality, and expropriable resources.

A Monetary Explanation of the Equity Premium, Term Premium, and Risk-Free Rate Puzzles

This paper develops and estimates a monetary model that offers an explanation of some puzzling features of observed returns on equities and default-free bonds. The key feature of the model is that some assets other than money play a special role in facilitating transactions, which affects the rate of return that they offer. The model is capable of producing a low risk-free rate, a high equity premium, and an average positive relationship between maturity and term premium for default-free bonds. The models implications for the joint distribution of asset returns, velocity, inflation, money growth, and consumption growth are also compared to the behavior of these variables in the U.S. economy.

Equilibrium in a production economy with an income tax

This paper develops a method to study an infinite-horizon production economy distorted by a state-dependent income tax. This setting permits taxes to depend on the capital stock, an endogenous state variable, and thus captures situations where the evolution for capital and taxes is jointly determined. To solve this model, the consumption function is represented as a fixed point of a nonlinear monotone operator that is defined such that its nth iteration computes the consumption function n steps away from the horizon for a corresponding finite-horizon economy. The oparators monotonicity is exploited in proving the existence of, and constructing, an equilibrium. Copyright 1991 by The Econometric Society.

Solving the Stochastic Growth Model by Policy-Function Iteration

This article describes a computer algorithm that solves the stochastic growth model by iterating on a fixed-point equation in the decision rule determining consumption as a function of the state variables. This algorithm does not discretize the state space, but rather it preserves the continuous domain of the capital stock and the productivity shock. The main advantge of this algorithm is that it is based on a Euler equation and thus it has a straightforward generalization to dynamic economies that cannot be solved by a central planner, such as a non-Pareto optimal competitive economy.

Welfare and optimum dynamic taxation of consumption and income

Abstract This paper estimates that the US could attain large welfare gains by implementing an optimal Ramsey tax policy that taxes consumption and income. It is also found that the welfare implications associated with taxing consumption are quantitatively more important than those associated with dynamically taxing income. Indeed, replacing income taxes with a constant consumption tax leads to a welfare gain that is only slightly lower than that attained by a dynamic policy that taxes consumption and income. In computing these welfare gains, careful attention is given to the dynamic path of tax rates and the transitional dynamics associated with how the economy responds to a new tax policy.

The U.S. Technology Frontier

In Caselli and Coleman (2000) we developed a framework that separately identifies the efficiency units embodied in unskilled labor, skilled labor, and capital in a country’s aggregate production function. Applying that framework to cross-country data, we showed that countries where unskilled labor is relatively abundant are those with the most efficient unskilled workers, while countries where skilled labor and capital are abundant are the most efficient users of these inputs. We interpreted these findings as evidence of appropriatetechnology adoption: in each country firms choose from a menu of technologies; different technologies imply different combinations of values for the efficiency units embodied in the three factors of production; in each country the technology is chosen that makes the most of the most abundant factors. In this paper we apply the same framework to time-series data from the United States over the period 1963–1992. We find that throughout this period the efficiencies of skilled labor and capital have risen. The efficiency of unskilled labor has risen in tandem with those of the other factors in the early part of the sample, but surprisingly, it has been falling since sometime in the 1970’s (the exact turning point depends somewhat on some parametric assumptions). In analogy with the cross-country evidence, these changes are closely associated with changes in the relative abundance of skilled labor and capital, which increased rather dramatically. In this sense, the recent history of technologies in use by U.S. firms may mimic the choice of technologies around the world today: as skills and capital become more abundant, technologies are chosen that maximize the efficiency of these inputs. As we discuss below, however, in the U.S. context the converse story (relative labor supplies adjusting to exogenous changes in technology) is also consistent with the data. Besides its relevance to models of technology adoption, this evidence also sheds new light on the widely documented recent increase in the skilled wage premium in the United States. Lawrence F. Katz and Kevin M. Murphy (1992) and David H. Autor et al. (1998) used the relative wage and the relative labor supply series to show that the efficiency of unskilled labor relative to skilled labor must have declined over time. Our framework allows us to go further and show that, indeed, the absolute efficiency of unskilled labor has fallen (after 1970), while the efficiency of skilled labor and capital have increased. A similar result was obtained with different techniques by Marta Ruiz Arranz (2001).

Uniqueness of an Equilibrium in Infinite-Horizon Economies Subject to Taxes and Externalities

Abstract This paper verifies the uniqueness of an equilibrium for a class of stochastic infinite-horizon economies with capital that are subject to distortionary taxes or externalities. The proof develops the property of concavity for a nonlinear monotone operator whose fixed points correspond to equilibria. As the underlying monotone operator has been useful for establishing the existence of an equilibrium, and for computing an equilibrium, this approach also brings under one roof the study of existence, uniqueness, and approximation of an equilibrium in distorted economies. Journal of Economic Literature Classification Numbers: C60, H20.

BEHAVIOR OF INTEREST RATES IN A GENERAL EQUILIBRIUM MULTISECTOR MODEL WITH IRREVERSIBLE INVESTMENT

The behavior of the real interest rate in a general equilibrium multisector model with irreversible investment is examined. It is shown that in such a model purely sectoral shocks can lead to substantial variation in the real interest rate and other aggregate time series. A source of variation in aggregate time series that is not found in one-sector models is thus examined, and the implications of this source of variation for the behavior of the interest rate are highlighted. Such a model seems to better capture the relationship among the real interest and output or investment than the standard one-sector stochastic growth model. It is also shown that, because of a desire to smooth consumption, with irreversible investment a rise in uncertainty concerning the future return to capital tends to lead to more current investment and a lower real interest rate.

Solving Nonlinear Dynamic Models on Parallel Computers

This paper describes an algorithm that takes advantage of parallel computing to solve discrete-time recursive systems that have an endogenous state variable.