《西北农林科技大学学报》70年发展史略

对《西北农林科技大学学报》创刊70年来的发展变迁历史进行了整理与回顾,简述了其创刊背景,并以其刊名变更为主线,将其发展过程分为初创与发行、确立与提高、稳定与发展、成熟与扩展4个阶段,对各个阶段的发展历史和特点进行了勾勒和分析,并对今后的发展目标进行了展望。     

Geography, demography, and early development

This paper explores the role of geography in early development. It presents a model where the odds of survival are higher in geographically favorable regions. In such regions, higher life expectancy prompts parents to devote more of their resources to old-age consumption and enables them to invest relatively more in the quantity and quality of their offspring. Investment in education, together with population growth, helps geographically-favorable economies to attain high levels of a more educated population that is necessary for sustained economic growth. The empirical evidence is generally supportive of the view that geographic attributes influenced regional population levels in Europe and its colonial offshoots around 1500 A.D. and that they affected population levels and educational attainment in low-income countries of the 1990s. For useful comments and suggestions I thank the editor, two anonymous referees, Daron Acemoglu, Ann Carlos, Phil Graves, Naci Mocan, Oded Stark, seminar participants at the University of Colorado at Boulder, the University of Colorado at Denver, and the 2002 Royal Economic Society Annual Conference. I owe a special debt of gratitude to my advisor Herschel Grossman who passed away in October 2004 after leaving his mark on many of us in the profession. The standard disclaimer applies. Responsible editor: Alessandro Cigno.     

Dynamic factor models

Summary Factor models can cope with many variables without running into scarce degrees of freedom problems often faced in a regression-based analysis. In this article we review recent work on dynamic factor models that have become popular in macroeconomic policy analysis and forecasting. By means of an empirical application we demonstrate that these models turn out to be usefu in investigating macroeconomic problems.     

The effect of mixing-distribution misspecification in conjugate mixture models

Parametric mixture models are commonly used in the analysis of clustered data. Parametric families are specified for the conditional distribution of the response variable given a cluster-specific effect, and for the marginal distribution of the cluster-specific effects. This latter distribution is referred to as the mixing distribution. If the form of the mixing distribution is misspecified, then Bayesian and maximum-likelihood estimators of parameters associated with either distribution may be inconsistent. The magnitude of the asymptotic bias is investigated, using an approximation based on infinitesimal contamination of the mixing distribution. The approximation is useful when there is a closed-form expression for the marginal distribution of the response under the assumed mixing distribution, but not under the true mixing distribution. Typically this occurs when the assumed mixing distribution is conjugate, meaning that the conditional distribution of the cluster-specific parameter given the response variable belongs to the same parametric family as the mixing distribution.     

Rate of strong uniform convergence of k-NN density estimates

Let f_n(x) be the univariate k-nearest neighbor (k-NN) density estimate proposed by Loftsgaarden and Quesenberry (1965). By using similar techniques as in Bahadur's representation of sample quantiles (1966), and by the recent results on the oscillation of empirical processes by Stute (1982), we derive the rate of strong uniform convergence of f_n(x) on some suitably chosen interval J_δ. Some comparison with the kernel estimates is given, as well as the choice of the bandwidth sequence relative to the sample size.     

Non-parametric recursive estimates of a probability density function and its derivatives

Recursive estimates of a probability density function (pdf) are known. This paper presents recursive estimates of a derivative of any desired order of a pdf. Let f be a pdf on the real line and p?0 be any desired integer. Based on a random sample of size n from f, estimators f^(p)_n of f^(p), the pth order derivatives of f, are exhibited. These estimators are of the form $\text{n}{}^{\mathrm{?1}}\text{∑n}\text{j=1}\text{δ}{}_{\mathrm{jp}}$, where δ_jp depends only on p and the jth observation in the sample, and hence can be computed recursively as the sample size increases. These estimators are shown to be asymptotically unbiased, mean square consistent and strongly consistent, both at a point and uniformly on the real line. For pointwise properties, the conditions on f^(p) have been weakened with a little stronger assumption on the kernel function.     

Three models of OPEC leadership and policy in the aftermath of Iran

Collapse of the Shah's regime has transformed Iran's attitude regarding oil production policy. The nature of OPEC leadership is changing as well. Three models examine the nature of this leadership inside OPEC: (1) the conventional price leadership model, (2) a model emphasizing a concept of egalitarian leadership, and (3) a team model composed of coalitions. The three models establish the limits within which OPEC leadership is exercised. A composite model drawing upon all three sets of results suggests that Saudi Arabia shapes cartel policy not by itself, but through a dominant coalition of states. For most of the period 1969–1978 this coalition has been stable. Following the unsettling changes of 1973, cooptation of Iran into the dominant coalition in 1974 was an important step in achieving a new level of stability. But during the turbulence of regime transformation in Iran, the nature of the governing coalition appears to have changed. One consequence may be that in the future Saudi Arabia will yield more willingly to arguments heard within OPEC on behalf of upwards price pressure, especially in an atmosphere of growing political isolation and overall tight supply.     

Debt management in a small open economy: A theoretical and an empirical study for Belgium

This article analyzes the effects of debt management and its consequence for the control of base money in a small open economy (Belgium). The study compares the effects obtained from a small theoretical model with the results of a larger empirical model.The theoretical model focuses on the financing of government by money operation, on the bond rate, and on the international reserve of the Central Bank.The empirical model is a medium-term one, including the demand and the supply sectors of the economy and permitting simultaneous analysis of real and financial variables.The effects of an endogeneous or exogenous debt management have been studied by numerical simulation of modification in the public expenditure, the world trade, and the discount rate.     

On UMVU estimators and Bhattacharya bounds in exponential distributions

A subfamily of exponential distributions is considered and it is shown that the variance of the UMVU estimator of an estimable function g(θ) having power series expansion is the limit of Bhattacharya bounds.     

On uniform approximation of Poisson variates by normal ones

In this paper the accuracy of the normal approximation to the Poisson is treated from the viewpoint of direct approximation of Poisson variables by normal ones. The conclusions that are derived on the accuracy of this approximation lead (among others) to very useful results on confidence limits for the mean of a linear combination of independent Poisson variables; these latter are employed in precise determination of the composition of a mixture of radioactive isotopes by means of a scintillation counter.