浅谈如何提高汽车的燃油经济性

目前,绝大多数汽车都是消耗燃油的,随着汽车保有量的增加,汽车消耗的燃油占石油产品消耗量越来越大,如何减少对石油产品的消耗,节约石油资源已成为举世瞩目的问题,而且从汽车使用的单位和个人角度来讲,降低燃油的消耗也是至关重要的,因此,我们有必要分析一下影响汽车燃油经济性的因素及提高汽车的燃油经济性的措施。     

Detecting nonlinearity in time series by model selection criteria

This article analyzes the use of model selection criteria for detecting nonlinearity in the residuals of a linear model. Model selection criteria are applied for finding the order of the best autoregressive model fitted to the squared residuals of the linear model. If the order selected is not zero, this is considered as an indication of nonlinear behavior. The BIC and AIC criteria are compared to some popular nonlinearity tests in three Monte Carlo experiments. We conclude that the BIC model selection criterion seems to offer a promising tool for detecting nonlinearity in time series. An example is shown to illustrate the performance of the tests considered and the relationship between nonlinearity and structural changes in time series.     

工具变量法综列单位根检验的有偏性及其修正

Chang（2002）基于非线性工具变量估计，提出了对截面相关综列数据进行单位根检验的SN检验，在综列数据生成过程不舍飘移和时间趋势时具有良好的表现。但我们的研究表明，在非平稳综列数据含有确定性趋势时，SN检验是有偏的，不再服从标准正态的渐近分布，而需要进行修正。本文基于蒙特卡罗仿真试验提出了一种简便的修正方法，修正后的SN检验统计量渐近分布为标准正态分布。仿真结果表明，修正后的SN检验具有更好的有限样本性质和较高的检验势。     

Distribution of residual autocorrelations for multiplicative seasonal ARMA models with uncorrelated but nonindependent error terms

In this paper, we consider portmanteau tests for testing the adequacy of multiplicative seasonal autoregressive moving‐average models under the assumption that the errors are uncorrelated but not necessarily independent. We relax the standard independence assumption on the error terms in order to extend the range of applications of the seasonal autoregressive moving‐average models. We study the asymptotic distributions of residual and normalized residual empirical autocovariances and autocorrelations under weak assumptions on noise. We establish the asymptotic behavior of the proposed statistics. A set of Monte Carlo experiments and an application to monthly mean total sunspot number are presented.     

A new method for measuring congestion in data envelopment analysis

In data envelopment analysis (DEA), there are two principal methods for identifying and measuring congestion: Those of Färe et al. [Färe R, Grosskopf S. When can slacks be used to identify congestion. An answer to W. W. Cooper, L. Seiford, J. Zhu. Socio-Economic Planning Sciences 2001;35:1–10] and Cooper et al. [Cooper WW, Deng H, Huang ZM, Li SX. A one-model approach to congestion in data envelopment analysis. Socio-Economic Planning Sciences 2002;36:231–8]. In the present paper, we focus on the latter work in proposing a new method that requires considerably less computation. Then, by proving a selected theorem, we show that our proposed methodology is indeed equivalent to that of Cooper et al.     

流动性约束下我国居民消费行为的二元结构与地区差异

本文构建了状态空间模型和跨省面板数据模型,就不确定性和流动性约束等对我国居民消费行为影响进行比较分析,结果表明:1978年以来,收入的不确定性对城镇居民消费行为的负面影响要大于农村居民;城镇居民面临的流动性约束相对小于农村居民;城镇居民面对利率的替代效应要大于收入效应,而农村居民与之相反。1995年以来,收入和支出的不确定性对我国居民整体消费行为的影响并不显著,但与东中部地区居民消费变动正相关;我国居民消费面临的流动约束整体来看并不严重,但中部地区居民相对而言面临更强的流动性约束。     

An empirical analysis of international labour migration in the Philippines

This study empirically investigates the impact of economic, demographic, and political factors on the size of emigration from the Philippines. In 2007, overseas workers from the Philippines sent remittances in excess of US$14 billion annually to their families back home. Although these remittances are an important source of foreign exchange and play an important role in economic development, the determinants of emigration in the Philippines are not well established. A simple unrestricted error correction model of migration was specified and estimated using data spanning the period 1975–2005. Results indicate that the level of unemployment, adult literacy and population density are the key determinants of emigration in the Philippines. The result also indicates that government instability impacts negatively on emigration in the Philippines. The policy implications of the results are discussed.     

Locally Most Powerful and Other Rank Tests for Independence – with a Contaminated Weighted Alternative

Several authors in the literature have attempted the quantification of the concept of stochastic dependence for bivariate distribution. Two weighted rank tests for testing independence against a weighted contamination alternative is proposed and their distributional properties are studied. We also derived a locally most powerful rank test for the alternative setting. The rank tests proposed are shown to be asymptotic locally most powerful for specific distributions.     

The Feldstein–Horioka puzzle in Latin American and Caribbean countries: a panel cointegration analysis

In this paper, the recently developed panel unit root and the Pedroni cointegration tests are applied to empirically examine the validity of the Feldstein–Horioka puzzle (F–H puzzle) for a heterogeneous panel of 14 Latin American and five Caribbean countries over the period, 1960–2002. The findings indicate that in these countries, the long-run solvency condition is maintained. Finally, employing the Pedroni panel group FM-OLS estimator (2000, 2001), it is found that the statistically significant estimated savings-retention coefficient for the panel is relatively small indicating that the F–H Puzzle is not valid and thus implying the prevalence of a moderate degree of capital mobility.

Spatial Nonstationarity and Spurious Regression: the Case with a Row-normalized Spatial Weights Matrix

Abstract

This paper investigates the spurious regression in the spatial setting where the regressant and regressors may be generated from possible nonstationary spatial autoregressive processes. Under the near unit root specification with a row-normalized spatial weights matrix, it is shown that the possible spurious regression phenomena in the spatial setting are relatively weaker than those in the nonstationary time series scenario. The regression estimates might or might not converge to 0. The divergence might occur only when the regressant has a near unit root much closer to unity than that of the regressor. For the t and F statistics, there could be over-rejection of the null of uncorrelatedness under certain situations, but they do not diverge. However, the coefficient of determination R ² converges to 0, which provides strong evidence of the spurious regression even when t and F statistics are large. Simulation results about different statistics are in line with the theoretical results we derive in this paper.

Non-stationnarité spatiale et fausse régression: l'argument pour la matrice de pondération spatiale à normalisation ‘row-normalized’

RÉSUMÉ?La présente communication se penche sur la fausse régression dans les cadres spatiaux, o[ugrave] des variables dépendantes et des variables explicatives peuvent être produites par d’éventuels procédés autorégressifs spatiaux non stationnaires. Dans le cadre de la spécification de la racine quasi-unitaire, avec une matrice de pondération spatiale normalisée ‘row-normalized’, il est démontré que les phénomènes de fausse régression dans les cadres spatiaux sont relativement plus faibles que ceux du scénario à série chronologique non stationnaire. Pour les statistiques t et F, on pourra assister à une sur-réjection du néant de la non corrélation dans certaines circonstances, mais aucune divergence. Toutefois, le coefficient de détermination R² converge vers 0, en apportant ainsi une preuve substantielle de la fausse, même en présence de statistiques t et F élevées. Les résultats des simulations sur différentes statistiques sont en accord avec les résultats théoriques que nous dérivons dans la présente communication.

No estacionariedad espacial y regresión falsa: el caso con la matriz de pesos espaciales standardizada por filas

RÉSUMÉ?Este trabajo investiga la regresión falsa en el ámbito espacial donde la variable dependiente y las variables independientes pueden generarse a partir de posibles procesos autorregresivos espaciales no estacionarios. Bajo la especificación de raíz unitaria con una matriz de pesos espaciales estandarizada por filas, se muestra que los posibles fenómenos de regresión falsa son relativamente más débiles que los del caso de la serie de tiempo no estacionario. En las estadísticas t y F, podría producirse un sobrerrechazo de la hipótesis nula de incorrelación bajo ciertas situaciones, pero no son divergentes. No obstante, el coeficiente de determinación R² converge a 0, lo que ofrece una evidencia fuerte de la regresión falsa incluso cuando las estadísticas t y F son amplias. Los resultados de simulación sobre diferentes estadísticas se mantienen en línea con los resultados teóricos que obtenemos en este trabajo.