Knowledge that Transforms

Increasing returns to scale (RTS) is frequently pos- tulated as affecting productivity in surface coal mining. How- ever, it is not clear whether increased capital intensity or increased output is the relevant phenomenon. A ray-homo- thetic production function that incorporates the capital-labor mix and fixed site geology into the scale elasticity is presented and estimated with a micro (mine level) dataset. The results indicate that higher capital intensity contributes to higher RTS for some types of capital equipment, but not all. On the average increasing RTS was found, with few mines approach- ing optimal scale. T HE literature of coal mining productivity contains many references to returns to scale as a factor in strip mining productivity.' However, different analysts use different definitions of scale,' and consequently their results are mixed. Some analysts associate returns to scale with larger pieces of capital equipment; 2 others use the more traditional economic notion of output volume and the scale elasticity;3 others simply relate output volume to labor productivity.4 It may be true that developments in large pieces of earth-moving equipment have been implemented at surface mines with large output volume, but this does not necessarily imply increasing returns to this par- ticular capital input. This confusion in the mining literature in the use of the term scale, coupled with the more general observation that large firms (not just large mines) rarely have the same capital-labor mix as their smaller counterparts, leads to a hypothesis that a different capital-labor mix yields different economies of scale. The application of ray-homothetic production functions leads to an easily testable hypothesis on the impact of input mix to economies of scale. Additionally, these functions are more general than their homothetic namesakes. Fare (1975) has shown that they do not generate linear expansion paths. convex isoquants, or exhibit strong dispos- ability of inputs. The properties of convexity and strong disposability are necessary for a dual, cost function analysis of the production structure. If the true underlying production function is ray- homothetic, the dual approach is inappropriate, therefore these functions are a desirable tool for productivity analysis in general and in particular when input mix is believed to be an important

Monte Carlo evidence is presented which supports the conclusion that when a block grants variable in an ordinary least squares (OLS) model is endogenously constructed due to the closed-ended nature of matching aid, estimates of the propensity to spend lump-sum aid are biased upward. The findings suggest that OLS estimates lead to erroneous conclusions regarding the existence of a flypaper effect and support the use of maximum likelihood models in situations where budget constraints are piecewise-linear.

Raymond S. Hartman, Product Quality and Market Efficiency: The Effect of Product Recalls on Resale Prices and Firm Valuation, The Review of Economics and Statistics, Vol. 69, No. 2 (May, 1987), pp. 367-372

Hope Corman, Theodore Joyce, Norman Lovitch, Crime, Deterrence and the Business Cycle in New York City: A VAR Approach, The Review of Economics and Statistics, Vol. 69, No. 4 (Nov., 1987), pp. 695-700

Because of the interdependent nature of family labor supply decisions, the nonnegativity constrai nt on women's hours of work will spill over into other consumption an d labor supply decisions of the family. Here the author develops an e conometric model of family labor supply that captures this "spillove r, " while addressing the usual censoring issues as well. The model i s based on a flexible direct utility function and permits unobservabl e differences in tastes. The model is estimated by the maximum likeli hood method on a sample of about 1, 200 families from the Panel Study of Income Dynamics. Copyright 1987 by MIT Press.

An econometric mod el is used to impute the value of time in the demand for medical care for member s of a prepaid group practice medical care program. Separate estimates are obtai ned for: (1) individuals who were employed full time, (2) housewives, and (3) ti me associated with taking children to a doctor. For individuals who were employe d full time, the estimate was close to the median wage rate. Sick leave was esti mated to substantially reduce the value of time. It was concluded that ignoring the time price of medical care may result in misleading statistical analysis and mistaken policy recommendations. Copyright 1987 by MIT Press.

The forecast performances of three groups of models of the inflation process are evalu-ated in this paper: ra tional expectations models with instantaneous market clearing, monetarist models , and expectations-augmented Phillips curves. The dynamic simulations performed for the intervals between 1977 and 1984 are somewhat discouraging for all three theories. The variation in forecasting performance within model groups often exc eeded the variation in performance across model groups. Nevertheless, the Philli ps curve formulation rarely performed worse than the other two models, and in th e 1981 to 1984 period it performed substantially better than the alternative mod els of inflation. Copyright 1987 by MIT Press.

In earlier studies, economic historians found that political goals, rather than social or humanitarian objectives, motivated much of New Deal spending. Using new information on annual, state level employment for the 1930s, this paper shows that, while politics are still important, responding to the needs of the unemployed was an important determinant of New Deal spending.

Kenneth E. Train, Daniel L. McFadden, Andrew A. Goett, Consumer Attitudes and Voluntary Rate Schedules for Public Utilities, The Review of Economics and Statistics, Vol. 69, No. 3 (Aug., 1987), pp. 383-391