The Construction of Residential Housing Price Indices: A Comparison of Repeat-Sales,Hedonic-Regression,and Hybrid Approaches

This article examines a number of hypotheses that underpin the repeat-sales and hedonic approaches to the construction of housing price indices, as well as the practical problems associated with the implementation of either approach. We also examine a hybrid procedure that combines elements of both the repeat-sales and hedonic-regression techniques. For our sample of individual home sales in Oakland and Fremont California over an 18-year period, repeat-sales methods are subject to sample selection bias; the maintained assumption of time constancy of implicit prices of housing attributes is violated; the repeat-sales estimator is extremely sensitive to influential observations; and the usual method used to correct for heteroskedasticity in repeat-sale housing returns is inappropriate in our sample. Hedonic techniques are better suited to contend with index number problems per se, as they can accommodate changing attribute prices over time. They also appear to give rise to more reliable estimates of price indices, as unusual observations have less effect on estimated price indices. Drawbacks of the hedonic approach include the usual concern with omitted attributes, and their effect on the estimated price index.     

活动图象压缩中的运动补偿算法研究

主要介绍活动图象压缩编码中最常用的几种运动补偿的算法——条件补充法和实现运动补偿技术的块匹配算法,梯度算法,傅立叶变化方法,其中也提出了用模糊数学处理方法,并指出,为了加快运动补偿向量的计算,搜索路径采取逐渐向外扩张的方式在运动较小的会议电视和可视电话中得到广泛应用;另一方法是计算象子块运动补偿时,只要所设定的(i,j)值的象块和原象块的相关系数达到一定的门限值就停止搜索,也会大大加快搜索的速度。     

武警部队后勤物资编码标准化的思考

针对武警部队现状,提出应用信息资源规划（IRP）的技术途径和方法建立武警部队物资编码标准,并对具体的实现方法提出了建议.     

遗传算法在配送中心选址中的应用

配送中心是现代物流的重要组成部分,它在整个物流系统中起着承上启下的作用,如何合理的选择配送中心就显得尤为关键.本文提出了一种新的二进制和浮点数混合编码的改进遗传算法.该算法对种群初始化函数和遗传操作做相应的改进,使得表示配送中心选址的决策变量只能在0或1这两个离散变量上选择,解码更加方便,大大提高了运算效率,改进的遗传算法能够很好的解决物流配送中心的选址问题.     

Towards a New Methodology of Estimating Party Policy Positions

In the last twenty years, an international group of political scientists has coded nearly 2000 party manifestos with the help of one single coding scheme based on 56 categories which covers all main topics of these documents. However, there is a growing awareness of the shortcomings of the underlying coding scheme, such as overlapping and missing categories, which cannot be repaired without coding all manifestos all over again. Some have presented an alternative for manifesto-research by means of expert opinions on party policy positions, but these are unable to provide reliable time series for subsequent election years. The unborn solution to some of the problems with the coding scheme would be the computerised content analysis on digitalised party manifestos. This would open up a new universe of infinite possibilities for recodings and reanalyses. The extended consequences from full computerisation of textual analysis are mind boggling. But at the present, these possibilities are merely potentials as the computerised techniques are still underdeveloped. This article explores the possibilities for computerised content analysis in such a way that all postwar manifestos in established democracies can be compared with each other with the help of flexible coding schemes.     

Question-Answer Sequences in Survey-Interviews

Interaction analysis was used to analyze a total of 14,265 question–answer sequences of (Q-A Sequences) 80 questions that originated from two face-to-face and three telephone surveys. The analysis was directed towards the causes and effects of particular interactional problems. Our results showed that problematic respondent behavior is affected by the questionnaire design, whereas inadequate interviewer behavior is affected by respondent behavior, rather than directly by the questionnaire design. Two surveys used questions for which validating information was available. It appeared that the occurrence of such irregularities of interviewer and respondent behavior was related to the validity of the eventual responses. Explanations for the occurrence of problematic respondent behavior were proposed, concerning both cognitive and conversational factors, related to the wording of questions and response alternatives. Part of this paper was presented at the International Conference on Questionnaire Development, Evaluation and Testing Methods, 14–17 November 2002, Charleston, South Carolina.     

Political Interference and Stock Price Consequences of Local Bias

Politics can interfere with capital markets. We show that political interference is a necessary condition for local bias in the stock market. We extend the framework of Hong, Kubik and Stein (2008) and find that the inverse relation between market‐to‐book ratios and the ratio of the aggregate book value of firms to the aggregate risk tolerance of investors in a state (RATIO) is only prevalent among firms located in areas where politics has substantial influence on local markets. Our results indicate that the impact of politically induced local bias is primarily demand driven and stronger among firms that are less visible.     

基于死亡率免疫理论的自然对冲有效性评估

为应对长寿风险对年金产品的影响,本文提出分段对冲策略,并以死亡率免疫和死亡率久期规则为理论基础探讨该策略的有效性问题。为避免传统久期匹配方法中参数估计误差的累积和传导,借助WinBUGS软件和贝叶斯Markov Chain Monte Carlo方法,在统一的计算框架下完成了死亡率预测、死亡率久期计算和对冲效果的数值模拟;并以4种分段组合准备金数据的三维图、方差缩减比(VRR)和VaR值为指标进行长寿风险对冲有效性的对比,结果表明低年龄寿险保单和高年龄年金保单组合具有最平滑的三维图,最小的VRR和VaR值,可明显提高长寿风险自然对冲的有效性。     

Two Decades of Commercial Property Returns: A Repeated-Measures Regression-Based Version of the NCREIF Index

This article documents 20 years of performance of commercial real estate in the United States using a portfolio of properties that comprise the widely followed NCREIF Property Index (NPI). We develop an extension of the repeated-measures regression (RMR) to produce an improved version of the NCREIF Index that eliminates the stale appraisal and seasonality problems. We use this RMR version of the index to examine the magnitude and duration of the of the crash in property values in the early 1990s. The RMR Index is also compared with the NAREIT Index, and property-type subindices are developed using a Bayesian estimator. Finally, it is also shown how the RMR can be used to estimate the average magnitude of random valuation error in commercial property valuation.     

基于邻近值的HEVC帧内预测优化

高性能视频编码(High Efficiency Video Coding,HEVC)标准中的帧内编码模式利用当前帧中像素点之间的空间相关性作出有效预测。为了解决待编码像素远离参考像素时预测不准确的问题,提出了一种基于邻近值的HEVC帧内预测优化算法。该算法的主要思想是,对于当前像素,先根据传统HEVC帧内编码方法得到其预测值,再使用该像素点左边、左上、上边位置的修正值以及该像素本身的预测值对该预测值进行修正。因为将当前像素与周围像素的相关性进行了有效的数学建模,所以HEVC帧内编码性能得到了提升。实验结果显示,所提算法与HEVC标准相比,最高节省了2.7%的码率,平均节省的码率为1.3%。