Knowledge that Transforms

[Estimates of parameters in Tobit and other models for limited, truncated and censored dependent variables are not robust against misspecification. A test of the standard assumptions against a general misspecified alternative in the univariate censored normal model is derived and extended to the Tobit regression case. Computational ease and freedom from specification of a specific alternative hypothesis are primary attractions of the test.]

Several procedures are proposed for testing the specification of an econometric model in the presence of one or more other models which purport to explain the same phenomenon.These procedures are shown to be closely related, but not identical, to the non-nested hypothesis tests recently proposed by Pesaran and Deaton [7], and to have similar asymptotic properties..They are remarkably simple both conceptually and computationally, and, unlike earlier techniques, they may be used to test against several alternative models simultaneously.Some empirical results are presented which suggest that the ability of the tests to reject false hypotheses is likely to be rather good in practice.

[The comparative statics of optimization models which have nonlinear constraints are examined. It is shown that most of the standard results of "linear" comparative statics still apply. However, it is also shown that individual substitution and income effects are systematically affected by the nature and degree of nonlinearity of the constraint. A model of quantity/quality trade-offs, previously examined in the literature, is analyzed, and several new results are developed.]

[This paper models the dynamics of the earnings distribution among successive generations of workers as a stochastic process. The process arises from the random assignment of abilities to individuals by nature, together with the utility maximizing bequest decisions of their parents. A salient feature of the model is that parents cannot borrow to make human capital investments in their offspring. Consequently the allocation of training resources among the young people of any generation depends upon the distribution of earnings among their parents. This implies in turn that the often noted conflict between egalitarian redistributive policies and economic efficiency is mitigated. A number of formal results are proven which illustrate this fact.]

[This paper emphasizes the importance of endogenous (price) uncertainty as distinct from the standard exogenous uncertainty about the state of the world. Markets where agents can enter into forward contracts contingent upon future spot prices are studied with respect to existence of equilibrium, occurrence of speculation, and efficiency.]

[Previous work in the demand for freight transportation has followed an aggregate approach without any consideration of the underlying behavior of the individuals who actually make mode-choice decisions. In this paper, we analyze mode-choice behavior at the level of the individual decision maker with the purpose of applying the results to various issues related to intermodal competition. Based on a theory of shipper/receiver behavior, a random expected utility model suitable for econometric analysis is developed and estimated. Data for the empirical analysis consists of a large number of shipments covering a wide range of commodities, lengths of haul, and origin-destination pairs. The transport modes considered in the analysis are regulated and unregulated motor freight and rail. The central conclusion is that each mode has an opportunity to attract a substantial amount of traffic in particular markets through either service or price competition. In general, however, it appears that the opportunities for attracting traffic are greater through lower rates than improvements in service quality.]

[This paper is concerned with characterizing the probability distributions that describe the (stochastic) stationary state of a neoclassical model of optimal growth. In particular, using both theoretical analysis and numerical simulation, we search for systematic relationships between savings (and investment) rates and variability of the economy's aggregates.]

[Competitive adjustment processes in labor markets where firms and workers are heterogeneous but well informed are studied. A natural notion of equilibrium for such markets is defined, and a plausible adjustment process is shown under reasonable assumptions always to converge to an equilibrium; this allows a generalization of several existence results in the literature. Finally, the relationship between market institutions (such as who makes offers) and which of the range of equilibria that heterogeneity makes possible arises, is studied. Generalizing results of Gale and Shapley and Shapley and Shubik, it is shown that all agents on a given side of the market agree on which is the best equilibrium, and that the equilibrium that emerges is the one most favored by the agents on the side of the market that makes offers in the adjustment process. The process can also be viewed as an algorithm for transportation and optimal assignment problems.]