Structure and understanding: Some observations on current activities in the field of structural modeling

Structural modeling has been under study in recent years as a method for dealing with complex societal problems, and is growing in acceptance as a tool for understanding complex social phenomena. Structural models demonstrate the interactions of the separate elements of a system and their combined overall effect. Thus, the nature of the problem for which this method of analysis is appropriate is different from complex problems of the traditional disciplines which lend themselves to reductionist approaches. This is because complex policy problems of society cannot be “solved” with precise analysis. Kenneth Boulding suggests that there are two ways to cope with a complex policy problem, either to “slice” the problem into partial equilibrium sections or “squeeze” it by aggregating numerous variables into a single index or macho variable. Structural modeling is an approach which comes under the general strategy of squeezing the problem and is promising because of the ability to include a range of macro variables which provide insights about social change. The articles in this issue treat several interesting aspects of this approach. In this article we wish to recall for consideration a central purpose for developing such methods. We have taken a historical approach to indicate some of the roots of the concern for the effect of technological process on social change. Within this context, we discuss the nature of the contributions made by the articles in this issue and what promise the methods offer to addressing the historical concern.     

Asymptotic confidence bands for the estimated autocovariance and autocorrelation functions of vector autoregressive models

This paper provides closed-form formulae for computing the asymptotic covariance matrices of the estimated autocovariance and autocorrelation functions of stable VAR models by means of the delta method. These covariance matrices can be used to construct asymptotic confidence bands for the estimated autocovariance and autocorrelation functions to assess the underlying estimation uncertainty. The usefulness of the formulae for empirical work is illustrated by an application to inflation and output gap data for the U.S. economy indicating the existence of a significant short-run Phillips-curve tradeoff.First version received: November 2002/Final version received: September 2003     

On the human aspects in structural modeling

This article deals with two facets of structural modeling often ignored: a) the several human roles that effective participative modeling must encompass, and b) the group procedures developed to assist modelers in defining the elements of the system to be modeled. The roles are 1) the method technician, 2) the facilitator, and 3) the participant. Their recognition on the part of the technology assessment leader is vital to the successful conduct of participative modeling. The element-generating group procedures surveyed here are organized into two categories: those which emphasize an atmosphere for free-wheeling thinking, and those which emphasize structured guidance (either through use of words or geometric and analytic techniques).     

On the theory of macroeconomic quasi-equilibria

Conclusion It has been shown that for the Classical System a quasi-equilibrium cannot exist, unless we make the ad hoc assumption of inflexible nominal wages⁸. The equilibrium in the classical regime corresponds to the general competitive equilibrium, and of course the validity of Walras' Law cannot be questioned. At the same time, however, it has been shown that to extend these conclusions to the Keynesian system as well is not justified. The Keynesian system has, in general, a quasi-equilibrium. The model constructed in this paper and the resulting conclusions are significant because the model: (a) Incorporates the Keynesian notion of effective demand, which includes the demand for capital goods (investment) as being performed by a group of people distinct from the consumers (and so, answering Negishi's point, there is a prince in Hamlet!), (b) Unlike other models (like the recent paper by Glustoff), it does not rely on nominal wage rigidity to explain unemployment, but instead, again answering Negishi's remark, it explains rather than postulates why real wages do not adjust in the presence of unemployment so as to eliminate it. (c) It verifies the validity of Clower's proposition that in the Keynesian System Walras' Law holds only in equilibrium. (d) It reconsiles Bent Hansen's original quasi-equilibrium model with the Keynesian proposition of an unemployment equilibrium, against the apparent view of Hansen that to do that would require the assumption of a Phillips curve, a view also shared by Arrow and Hahn, and many others.An earlier version of this paper was presented in the December 1974 meeting of the Econometric Society in San Francisco. The author wishes to thank Prof. R. Clower, Prof. B. Hansen, Prof. S. Black, and Dr. G. Winckler for their valuable comments, but he obviously claims any errors for himself.     

Investigating the solvency of brazilian credit unions using a proportional hazard model

Abstract ** : Due to high interest rates and bank spreads, the number of credit unions in Brazil has increased over recent years. As financial institutions, these cooperatives need tools to signal impending financial problems. This paper focuses on one tool that can be used to evaluate credit union solvency: the Cox Proportional Hazards Model. A sample of 80 credit unions from the Brazilian state of Minas Gerais was selected to supply data. The analysis period is between December 2001 and June 2003. The results indicate that the relevant indicators for insolvency prediction are, in descending order of predictive ability, General Liquidity, Salary and Benefit Expenses, and the Loan/Equity Ratio. In general, results produced using the delineated theoretical model were in consonance with international literature .     

Two–step sequential sampling

Choosing the sample size in advance is a familiar problem: often, additional observations appear to be desirable. The final sample size then becomes a random variable, which has rather serious consequences.
Two such sample extension situations will be considered here. In the first situation, the observed sample variance determines whether or not to double the original sample size. In the second situation, the variances observed in two independent samples are compared; their ratio determines the number of additional observations.     

Time variation in the cointegrating relationship between stock prices and economic activity

The present paper examines whether there exists a long‐run cointegrating relationship between a stock market index and output and interest rates. Moreover, estimation is conducted over the full sample and both a recursive and rolling sample to examine any time variation in the nature of the relationship. The results support evidence of a single cointegrating vector, where stock prices typically exhibit a positive relationship with industrial production and a negative relationship with interest rates. However, there is significant time variation and periods of time where contrary results are observed. As such any model of stock prices needs to account for such time variation     

A theory of natural addiction

Economic theories of rational addiction aim to describe consumer behavior in the presence of habit-forming goods. We provide a biological foundation for this body of work by formally specifying conditions under which it is optimal to form a habit. We demonstrate the empirical validity of our thesis with an in-depth review and synthesis of the biomedical literature concerning the action of opiates in the mammalian brain and their effects on behavior. Our results lend credence to many of the unconventional behavioral assumptions employed by theories of rational addiction, including adjacent complementarity and the importance of cues, attention, and self-control in determining the behavior of addicts. We offer evidence for the special case of the opiates that “harmful” addiction is the manifestation of a mismatch between behavioral algorithms encoded in the human genome and the expanded menu of choices faced by consumers in the modern world.