Empirical testing of alternative price spread models in the South African maize market

Reduced-form price spread models have been recently utilized by Wohlgenant and Mullen, and Thompson and Lyon to evaluate the economic factors affecting the marketing margins for agricultural products. Drawing on Gardner, Heien, Buse and Brandow, Waugh, Tomek and Robinson, and others they specify alternative retail-farm price spread models and attempt to determine which best fit the data in the context of underlying theoretical rationale. This paper continues in the spirit of Wohlgenant and Mullen, and Thompson and Lyon by evaluating alternative specifications of the retail-farm price spread for white maize in South Africa. However, several important differences do remain. Wohlgenant and Mullen analyzed the price spread for beef using annual data, while Thompson and Lyon modeled the price spread for oranges using weekly data. The time period under consideration can be expected to affect the choice of model because fixed markup rules that might be evident using a short-run period of analysis (e.g., Thompson and Lyon) become untenable over the long run with underlying supply and demand shifts. In this paper, monthly data, which may be interpreted as an intermediate-run period, are used along with dichotomous supply-demand shifters. In addition, Brorsen et. al. have shown that price uncertainty affects the price spread in the marketing channels of agricultural commodities. Thus, the analysis in this paper extends the framework of Wohlgenant and Mullen, and Thompson and Lyon to include measures of price risk. Finally, like Brorsen et. al. this study pertains to the grain market, while Wohlgenant and Mullen, and Thompson and Lyon studied the marketing margin for non-storable commodities.     

Relationship of direct nursing care hours to DRG and severity of illness

Great variation in nursing resource use is documented within DRGs. Much of this variation may be explained by patient severity of illness. Variance in nursing resource use within DRGs can be reduced by using a severity of illness instrument to score patients.     

Copyright Damages and Statistics

This paper discusses the statistical issues that arise in conducting an economic damages analysis in the context of a litigation matter involving copyrights. Calculating damages in copyright cases turns out to be a natural application for econometric modelling methods. Surprisingly, elementary statistical issues can be a source of significant debate between the experts in such matters. In this paper, we present a case study and illustrate how issues such as interpretation of p -values and what "rejection of the null hypothesis" really "means" in such matters.     

Improved estimation of portfolio value‐at‐risk under copula models with mixed marginals

Portfolio value‐at‐risk (PVAR) is widely used in practice, but recent criticisms have focused on risks arising from biased PVAR estimates due to model specification errors and other problems. The PVAR estimation method proposed in this article combines generalized Pareto distribution tails with the empirical density function to model the marginal distributions for each asset in the portfolio, and a copula model is used to form a joint distribution from the fitted marginals. The copula–mixed distribution (CMX) approach converges in probability to the true marginal return distribution but is based on weaker assumptions that may be appropriate for the returns data found in practice. CMX is used to estimate the joint distribution of log returns for the Taiwan Stock Exchange (TSE) index and the associated futures contracts on SGX and TAIFEX. The PVAR estimates for various hedge portfolios are computed from the fitted CMX model, and backtesting diagnostics indicate that CMX outperforms the alternative PVAR estimators. © 2006 Wiley Periodicals, Inc. Jrl Fut Mark 26:997–1018, 2006     

Permanent magnets: a technological analysis

Abstract
Technology analysis is a new technomanagerial discipline that provides common frameworks for analysing individual technologies and their relationships to each other. It is used here to probe the development of a particular technology, namely that of permanent magnets.
The paper traces the development of permanent magnets over the past decade and explores possible future improvements in performance parameters. The strength of magnets (i.e. energy product as expressed in kilo Joules per cubic metre) has increased from approximately 40 in the 1930s to approximately 400 at present.
Future developments will be constrained by a barrier which seems to exist at approximately 525 kilo Joules per cubic metre. However this is viewed as a barrier that can be transcended and not as an immutable limit. It therefore signifies a possible breakthrough zone.
S-curve theory leads analysts to speculate about a possible breakthrough during the five year period leading up to 1995. At that date magnetic strengths of 600+ kilo Joules per cubic metre could be aimed for.
Increased magnetic strength will improve the performance parameters of all technologies utilising magnets, unleash new magnetic based technologies and threaten many traditional areas in the fields of matter processing, transporting and storing, energy processing, and information processing and storing.
These effects will cascade through the entire technological landscape creating new markets and destroying others. The article gives an overview of these impacts on the technological landscape.     

Regulatory Monitoring and the Impact of Bank Holding Company Dividend Changes on Equity Returns

This paper examines the impact of announcements of dividend changes by bank holding companies (BHCs) on equity returns. Many empirical studies of dividend behavior reveal positive market responses to dividend increases, which have been interpreted as confirmation of the signalling theory of dividend behavior. These studies typically focus on “large” changes, however. We argue that BHCs allow for a stronger test of signalling theory because regulatory monitors, in effect, “certify” dividend signals. Consequently, even “small” dividend increases should result in positive abnormal equity returns. Using the event study methodology, our results generally confirm this hypothesis for a sample covering the period 1973–1987.     

PRINCIPAL AND AGENCY TRADES BY STOCKBROKERS ARE COMPLEMENTARY: THE WELFARE EFFECTS OF DEREGULATING AGENCY TRADING AND BANNING PRINCIPAL TRADES

This paper models the demand for stockbrokers' services in Australia, consisting of two related services, agency trades and principal trades. The relationship between agency and principal trades is estimated. The results indicate that the two services are complements rather than substitutes. Using unique accounting information, a model of agency and principal trading activities is estimated to determine the welfare effects of (i) deregulating brokerage commissions and (ii) a ban on principal trading by brokers. The results show a sizeable welfare gain to investors (amounting to about 60% of the gross revenue of brokers) stemming from deregulation of the minimum charge for agency trades. The loss in profitability by brokers due to deregulation is also computed and shown to be negligible. The results also show that due to complementarity, a ban on principal trading, even with deregulation of agency trading, can impose an arbitrarily high cost on investors which could, in principle, offset the gains from agency deregulation.     

Fixed Exchange Rates and Disinflation in Emerging Markets: How Large Is the Effect?

We examine developing countries which have institutional quality ratings for the effects of exchange rate rigidity on inflation. The level of institutional development exerts no effect on the impact of currency regimes. However, the interaction of institutional quality and exchange rates has, in the most plausible specifications, a negative impact on inflation. This suggests that fixed exchange rates exert at most a contingent effect on inflation, and indicates that countries in Eastern Europe and Latin America contemplating currency pegs would be better off improving institutional quality prior to adopting the euro or dollar and expecting a large subsequent disinflationary effect. JEL no.  F31, O11