Testing for PPP: Should we use panel methods?

A common finding in the empirical literature on the validity of purchasing power parity (PPP) is that it holds when tested for in panel data, but not in univariate (i.e. country-specific) analysis. The usual explanation for this mismatch is that panel tests for unit roots are more powerful than their univariate counterparts. In this paper we suggest an alternative explanation. Existing panel methods assume that cross-unit cointegrating relationships, that would tie the units of the panel together, are not present. Using simulations, we show that if this important underlying assumption of panel unit root tests is violated, the empirical size of the tests is substantially higher than the nominal level, and the null hypothesis of a unit root is rejected too often even when it is true. More generally, this finding warns against the automatic use of panel methods for testing for unit roots in macroeconomic time series.First version received: November 2001/Final version received : October 2003     

TESTING FOR STATIONARITY WITH A BREAK IN PANELS WHERE THE TIME DIMENSION IS FINITE

In this paper, we consider the case of finite time dimension in the panel stationarity tests with structural breaks. By fixing T, the finite sample properties of the tests for both micro (T small and N large) and macro (both T and N large) panel data are generally greatly improved. More importantly, the derivation of the tests for finite T and , as opposed to joint asymptotic where N and simultaneously, avoids the imposition of the rate condition making the test valid for any (T, N) blend. Four models corresponding to the usual combination of breaks are considered. The asymptotic distributions of the test are derived under the null hypothesis and are shown to be normally distributed. Their moments for T fixed are derived analytically employing Ghazal’s corollary 1. The case with unknown breaks is also considered. The proposed tests have generally empirical sizes that are very close to the nominal size. The Monte Carlo simulations show that the power of the test statistics increases substantially with N and T.     

国有单位工资结构及其就业规模变化的收入分配效应:1988—2007

本文使用1988年、1995年、2002年、2007年CHIP城镇入户调查数据考察国有单位工资结构及其就业规模变化的收入分配效应。为此,本文采用了分位数回归方法、以多重分位数回归为基础的Machado&Mata(2005)反事实分解方法及作者扩展了的方法。各结果表明:国有企业就业份额大幅度下降导致中国城镇工资收入差距显著下降;然而国有企业减员增效改革完成以后,国有企业工资高于非国有企业的幅度及其不合理部分大幅度上升,其结果是城镇工资收入差距扩大。     

Has Inflation Persistence Changed under EMU?

This paper analyzes the persistence of inflation in the euro area and, in particular, whether the persistence properties have changed since the start of European Monetary Union(EMU). For that purpose, we compare pre‐ and post‐EMU inflation persistence, use rolling‐window estimates of persistence, and apply tests specifically designed to detect break dates near the end of the sample period. In contrast to previous research, we find that inflation persistence has fallen significantly since the start of EMU. Persistence of consumer price inflation, which is central to the European Central Bank's policy mandate, has fallen more than the persistence of deflator inflation. The drop in inflation persistence is consistent with the results from a simulated small New Keynesian model with a shift toward a more aggressive monetary policy stance.     

液体腰轮流量计示值误差测量结果的不确定度评定

结合中国石油长庆油田分公司原油流量计量的实际,利用测量不确定度评定的知识,通过建立数学模型、分析各输入量的标准不确定度、合成标准不确定度及扩展不确定度、给出测量不确定度报告,以达到对液体腰轮流量计示值误差测量结果的不确定度评定的目的。     

对外直接投资与经济增长关系研究——以湖南经济为例

本文的目的是通过湖南省对外直接投资与经济增长的关系的定量分析,得出一些实证关系,从而对湖南对外直接投资的作用有更精确的掌握,对于湖南贸易及投资的发展提供理论及政策导向.研究表明,湖南对外直接投资是贸易变化的原因,而贸易不是对外直接投资变化的原因.     

Does a non-linear mean reverting process characterize real GDP movements?

This paper uses non-linear models to investigate non-stationarity of real GDP per capita for seven OECD countries over the period 1900–2000. Unit root tests based on non-linear models are more powerful than traditional ADF statistics in rejecting the null unit root hypothesis. Empirical results show that, contrary to what the linear ADF statistics suggest, stationarity characterizes five out of the seven countries. This finding stands at variance with other recent studies which conclude that movements in real GDP per capita can be characterized as a non-stationary process.

Innovation dynamics in the EU: convergence or divergence? A cross-country panel data analysis

This paper investigates whether a convergence or divergence of national innovation capabilities of the 15 EU countries occurs in the course of time. An answer to this question permits immediate conclusions with regard to the success prospects of a convergence of per capita incomes and labor productivities within the EU. For the empirical analysis based on patents granted at the US-Patent and Trademark Office, unit root tests for time series and panel data are used to scrutinize the convergence hypothesis. Taking all results together, evidence points to the fact that an absolute convergence of innovation capabilities is an exception. However, for a number of countries the results suggest either conditional convergence or convergence to their own growth paths.

氮,磷,钾配合施用对人参质量影响的研究

利用正交试验设计给人参配施氮、磷、钾肥在鲜根重量和人参药效成分－－人参皂甙含量啬的基础上，找出最佳施肥处理组合，用以探讨氮，磷，钾肥与人参质量的关系。     

美中贸易收支与人民币汇率关系:实证分析

针对美中贸易收支与人民币汇率问题,经研究发现,汇率变动对贸易收支的影响是值得怀疑的,仅仅依靠人民币汇率变动是无法解决美中贸易逆差问题的。1994—2002年年度数据实证显示,美中贸易收支与人民币汇率(名义或实际汇率)之间没有稳定的关系;1998—2003年月度数据计量表明,美中贸易收支与人民币汇率之间没有长期稳定的协整关系。并且,依据美中两国月度统计数据计量的结论是相一致的。因此,“人民币升值论”或许更多的是基于政治而非经济因素,人民币汇率浮动并不能解决美中贸易逆差问题。