Empirical tests to discern linkages between construction and other economic sectors in Singapore

The construction industry makes significant contributions to the socio-economic development process in most countries. Its importance in the economy is due largely to the direct and indirect impact it has on the national economy. It stimulates the growth of other sectors through a complex system of linkages. Interest in multi-sectoral linkages was generated following Hirschman's work that investigated the relationship between unbalanced sectoral growth and economic development. Most of the past research work had used Leontief's input-output analysis to gauge the backward and forward linkages between industries. This paper proposes an econometric procedure that can be used for determining the construction output linkages. This involves unit-root testing and Granger causality testing. The main purpose is to determine the impact of a fluctuation in construction output on the sectoral production and the economy of Singapore. This helps to assess the role of the construction industry and how it is affected by the changes in the other economic sectors.     

Assessing causality in multivariate accident models

This paper discusses the application of operational criteria of causality to multivariate statistical models developed to identify sources of systematic variation in accident counts, in particular the effects of variables representing safety treatments. Nine criteria of causality serving as the basis for the discussion have been developed. The criteria resemble criteria that have been widely used in epidemiology. To assess whether the coefficients estimated in a multivariate accident prediction model represent causal relationships or are non-causal statistical associations, all criteria of causality are relevant, but the most important criterion is how well a model controls for potentially confounding factors. Examples are given to show how the criteria of causality can be applied to multivariate accident prediction models in order to assess the relationships included in these models. It will often be the case that some of the relationships included in a model can reasonably be treated as causal, whereas for others such an interpretation is less supported. The criteria of causality are indicative only and cannot provide a basis for stringent logical proof of causality.     

Market integration and price transmission in the U.S. natural gas market: From the wellhead to end use markets

Examination of the upstream-downstream pricing behavior in U.S. natural gas industry reveals that: (a) natural gas markets are integrated but subject to regime shifts and asymmetric adjustments, suggesting market imperfections. (b) Demand- and supply-side shocks play important roles in determining short-run price movements as evidenced by tests of causality and impulse response functions. (c) The response of end use prices to deviations from equilibrium with wellhead prices vary. Electrical, industrial and city gate prices adjust fast while commercial and residential prices adjust slowly, consistent with the role of administered pricing in later markets. (d) Long-run variations in end use prices are primarily due to their own shocks, while long-run variations in wellhead prices are due to innovations in residential and electrical prices. These findings point to the importance of demand shocks as the primary determinant of natural gas prices in the long-run.     

Synchronous,asynchronous, and causally ordered communication

Summary.  This article studies characteristic properties of synchronous and asynchronous message communications in distributed systems. Based on the causality relation between events in computations with asynchronous communications, we characterize computations which are realizable with synchronous communications, which respect causal order, or where messages between two processes are always received in the order sent. It is shown that the corresponding computation classes form a strict hierarchy. Furthermore, an axiomatic definition of distributed computations with synchronous communications is given, and it is shown that several informal characterizations of such computations are equivalent when they are formalized appropriately. As an application, we use our results to show that the distributed termination detection algorithm by Dijkstra et al. is correct under a weaker synchrony assumption than originally stated. Received: November 1992/Accepted: July 1995     

What do we mean by responsibility? The case of UK housing benefit reform

There have been increasing attempts by the UK government to link welfare provision to personal responsibility, trying to alter behaviour through the introduction of new policy instruments. This paper explores what it means to be responsible and what implications this has for policy. The first part of the paper discusses the UK government’s 2002 proposals to reform Housing Benefit and how the document refers to responsibility. In the second part I discuss what we mean by responsibility and explore some of the philosophical complexities of the concept. In the final part of the paper I attempt to suggest what form of responsibility is implied in the reform proposals and what implications this has for the proposed policy.     

Master curve of viscoelastic solid: Using causality to determine the optimal shifting procedure,and to test the accuracy of measured data

Viscoelastic solids such as rubber exhibit a complex elastic modulus E(ω), which depends on the frequency ω of the applied stress or strain. The modulus E(ω) can often be determined in a wide frequency range by performing measurements in a limited frequency range for many different temperatures, and then shift the frequency segments horizontally along the frequency axis to obtain a continuous master curve. We show that one can use the spectral representation of E(ω) (or 1/E(ω)), which obeys causality, to determine the optimal shifting procedure, and to test the accuracy of the measured data and the calculated master curve.     

基于因果图的一种推理算法

针对因果图推理中存在逻辑运算量大、计算复杂的困难，提出了一种基于因果图的特性的新的推理算法。该方法先将因果图转化为一系列因果树，然后在上直接进行推理，避免了将因果图进行割集展开，从而有效地降低了因果图推理的复杂度，提高了因果图推理的计算速度。     

Electricity consumption and economic growth: a time series experience for 17 African countries

While the availability of electricity by itself is not a panacea for the economic and social problems facing Africa, the supply of electricity is nevertheless believed to be a necessary requirement for Africa's economic and social development. This paper tests the long-run and causal relationship between electricity consumption per capita and real gross domestic product (GDP) per capita for 17 African countries for the period 1971–2001 using a newly developed cointegration test proposed by Pesaran et al. (2001) and using a modified version of the Granger causality test due to Toda and Yamamoto (1995). The advantage of using these two approaches is that they both avoid the pre-testing bias associated with conventional unit root and cointegration tests. The empirical evidence shows that there was a long-run relationship between electricity consumption per capita and real GDP per capita for only 9 countries and Granger causality for only 12 countries. For 6 countries there was a positive uni-directional causality running from real GDP per capita to electricity consumption per capita; an opposite causality for 3 countries and bi-directional causality for the remaining 3 countries. The result should, however, be interpreted with care as electricity consumption accounts for less than 4% of total energy consumption in Africa and only grid-supplied electricity is taken into account.     

Bi-directional causality in California's electricity and natural-gas markets

The Granger instantaneous-causality test is applied to explore the potential causal relationships between wholesale electricity and natural-gas prices in California. The test shows these relationships to be bi-directional, and reveals California's electricity and natural-gas markets to be as inextricably intertwined as casual observation and theoretical considerations would suggest they ought to be. This meshing of markets exacerbated the effects of California's natural-gas crisis on the contemporaneous electricity crisis, while concurrently the electricity crisis may have contributed to the dysfunction in the national-gas market and helped to precipitate the natural-gas crisis. The finding supports an integrated approach, as opposed to a piecemeal approach, for formulating energy policy recommendations, not just in California but in the world at large.     

基于模糊因果图的故障诊断

因果图理论是一种基于概率论的不确定推理模型,能够进行在线动态推理和对复杂系统进行故障诊断,但在因果图模型中,要求事件的发生概率为精确值.针对实际情况事件发生概率具有模糊性和不确定性的特点,文章将模糊数引入因果图中,解决了获取事件发生概率精确值的难度,又使因果图能处理带模糊性和不确定性的问题.实例表明,该方法不但比故障树分析(FTA)更有效,而且能进行故障树分析不能进行的诊断推理和辩解推理.