A method for calculating changes in regression coefficients and inverse matrices corresponding to changes in the set of available data

Abstract

Extract

When we have made a regression analysis, for instance on the basis of time series, it is often of interest to know how the results would change if we take into account observations made later on. Because it seems that the whole work of solving the normal equations must be made over again, we seldom continue the calculations by taking into account later information. It is, however, easy to find the adjustments required by a method developed in this article. It is possible to get time series showing the development of the regression coefficients without formidable work. We can in this way get a deeper insight in the problem to be studied than by making the regression analysis only once for all. If the purpose of the regression analysis is to obtain formulas to be used for forecasting, time series of regression coefficients give a better starting point than if we only have regression coefficients for a certain period.     

On the first passage time processes of brownian motion with positive drift

Abstract

The first passage time processes of Brownian Motion with positive drift are of considerable importance, particularly in life-testing or life-time situation as a natural consequence. It has been used in sequential analysis, e.g. finding the best test for testing the hypothesis of no drift versus the alternative of positive drift in a Brownian Motion. Various properties of the first passage time process of Brownian Motion with positive drift are reviewed and several new properties are investigated. In short, γ-variation properties, characterization, and behaviour at infinity are discussed.     

On de-seasonalising adjusted-average formulae

The techniques of Borgan (1979) are extended to cover data with seasonal variations. Examples are given, and it is suggested that the formulae presented here give smoother results than those traditionally employed to deal with economic time series subject to seasonal variations.     

Vector Autoregression on Nigerian Money and Agricultural Aggregates

This paper employs a sophisticated time series technique, vector autoregression (VAR) to study the effects of domestic credit conditions proxied by money supply (M1 and alternatively, M2), on domestic prices and agricultural trade. For the period Nay 1970 to December 1979, the time series data admit a four-lag specification for the VAR system containing M1, total value of agricultural exports (AGE), total value of agricultural imports (AGI), and consumer price index (CPI) as well as the system containing M2, AGE, AGI and CPI. This study found that both M1 and M2 have statistically significant impacts on the agricultural and price variables. More interesting, this study found that unexpected changes in both M1 and M2 (defined as random monetary shocks) have perceptible influence on agricultural and price variables. By and large, the empirical results of this paper strongly support the contention that money matters for the agricultural sector of Nigeria. Cet article emploie une technique sophistiquée de séries de temps, le vecteur d'autoregression (VAR) pour étudier les effets des conditions de crédits domestiques dus à la masse monétaire (M1 et alternativement, M2), sur les prix domestiques et le commerce agricole. De la période de Mai 1970 à Decembre 1979, les données des séries de temps ont admit un “four-lag specification” au systeme VAR contenant M1, la valeur totale des exportations agricoles (AGE), la valeur totale des importations agricoles (AGI) et l'indice des prix à la consommation (CPI) aussi bien que le système contenant M2, AGE, AGI et CPI. Cette étude a trouvé que tous les deux M1 et M2 ont des impacts statistiquement significatifs sur les variables agricoles et de prix. Plus intéressant encore, cette etude montre que des changements imprévus en M1 et M2 (définis comme chocks monétaires au hazard) ont des influences perceptibles sur les variables agricoles et de prix. En somme, les résultats empiriques de cette étude supportent fortement le contentieux selon lequel l'argent est important au secteur agricole du Nigeria.     

Labour trends in agriculture: The case of the summer rainfall grain‐producing area

The impact of changes in the labour force on commercial agriculture has received little systematic research attention. In this study the major trends in the post‐war years are described and analysed. It is shown that there has been an increasing substitution of labour for capital over the past fifteen years. The causes of this substitution trend are identified, and it is shown that these should be taken into account in the formulation of farm policy. Labour trends in commercial agriculture also have implications for the broader Southern African economy, and some tentative remarks in this regard serve as motivation for further research.     

Problems and lessons from irrigation projects in less developed countries of Africa

This paper reviews important constraints to the development of small‐holder irrigation schemes in less developed areas of Africa. It is based on two case studies from Southern Africa and experience elsewhere on the continent. Lessons from past experience and the institutional and human development considerations required for successful projects are discussed.     

Employment adjustment in two countries with poor reputations: Analysis of aggregate, firm, and flow data for Portugal and Germany

This paper supplements aggregate time-series analysis of the speed of employment adjustment with evidence from firm panel and flow data for two countries – Portugal and Germany – sharing unenviable labor market reputations. The Portuguese labor market is often portrayed as terminally inert, while that of Germany as badly ailing. We report broad consistency in the results across data sets in favor of Portugal. In benchmarking Portugal against Germany, the adverse reputation of the former – if not necessarily that of the latter country – may have been exaggerated in contemporary policy debate.We thank, without implicating, two anonymous reviewers of this journal for their helpful remarks on an earlier version of the paper.     

让援助更为明智

为全世界儿童提供初等学校教育将是一项漫长而且耗费甚大的工程。幸好，自1990年以来，主要的捐助者极大地增加了他们对于总体教育，特别是初等教育的官方发展援助（ODA）。2003年对所有教育目标的捐赠承诺额达到了67亿美元，是6年前承诺额真实数量的两倍以上。对于初等教育的承诺额增加得甚至更快，在1990—2003年间增长了四倍，达到19亿美元。对于初等教育的援助比总体ODA增长的更快，其在承诺额中的份额从1990年的0．4％增长到2003年的1．9％（见图1和图2）。     

The FTC in the 1980s

This paper reviews the antitrust activities of Federal Trade Commission during the 1980s with special emphasis on the role of economics and economists. We contrast the FTC during the 1980s to its record in the 1970s and conclude that the agency was more active during the 1980s than is popularly believed. Perhaps more significant than changes in the level of enforcement activity was the agency's move to a more economics-oriented approach to antitrust enforcement and an increased role for Commission economists. The paper also comments on what FTC economists learned about American industry during the 1980s.