Interstate migration in Mexico: variations on the Todaro theme

"This study of migration in Mexico is based upon a modified Todaro approach and utilizes census data in a simultaneous equations model of 13 variables. It is unique in several ways: (a) it introduces proxy variables for employment probability and cost of migration that have not heretofore been found in the literature, but for which data are often available; (b) it illustrates that in some important cases census data have advantages not available through surveys; and (c) it finds that in some sense land reform in Mexico may have operated perversely. Finally, the study opens a new avenue for the study of informal sector growth."     

Organisation strategies and industrial relations

Stuart Timperley discusses two important themes in the management of industrial relations in organisations: firstly, that it is possible, through managerial decisions and actions, to influence industrial relations and, secondly, that a case can be made for such decisions and actions to be implemented.     

Portfolio choice and equilibrium in capital markets with safety-first investors

This paper develops optimal portfolio choice and market equilibrium when investors behave according to a generalized lexicographic safety-first rule. We show that the mutual fund separation property holds for the optimal portfolio choice of a risk-averse safety-first investor. We also derive an explicit valuation formula for the equilibrium value of assets. The valuation formula reduces to the well-known two-parameter capital asset pricing model (CAPM) when investors approximate the tail of the portfolio distribution using Tchebychev's inequality or when the assets have normal or stable Paretian distributions. This shows the robustness of the CAPM to safety-first investors under traditional distributional assumptions. In addition, we indicate how additional information about the portfolio distribution can be incorporated to the safety-first valuation formula to obtain alternative empirically testable models.     

Hypothesis testing based on goodness-of-fit in the moving average time series model

Small sample properties of t-tests are compared with those of tests based on relative goodness- of-fit in the context of the first order moving average time series model. Monte Carlo experiments reported in the paper suggest that the actual size of these t-tests greatly exceeds theoretical large sample significance levels, while conformity of goodness-of-fit statistics to the appropriate chi-square or F-distributions is much closer. The evidence presented suggests that practitioners are well advised to employ goodness-of-fit tests as a check on results of t-tests particularly when the latter indicate ‘significance’.     

A LINEAR PROGRAMMING SOLUTION TO SOME MARKET ALLOCATION PROBLEMS

Certain market allocation problems involving linear average net revenue functions can be solved by linear programming. The technique can be applied to an objective function derived from linear marginal net revenue functions, the objective being to force each marginal net revenue as near to zero as possible given the constraint set. If a particular problem is suited to a linear programming solution, researchers may prefer to use this technique rather than more sophisticated optimization methods.