The long memory model of political support: some further results

This paper extends the results of Byers, Davidson and Peel (1997) on long memory in support for the Conservative and Labour Parties in the UK using longer samples and additional poll series. It finds continuing support for the ARFIMA(0,d,0) model though with somewhat smaller values of the long memory parameter. We find that the move to telephone polling in the mid-1990s has no apparent effect on the estimated value of d for either party. Finally, we find that we cannot reject the hypotheses that the parties share a common long memory parameter which we estimate at around 0.65.

Addressing unobserved selection bias in accounting studies: the bias minimization method

This note explains the minimum-biased estimator (MBE), which accounting researchers can use to analyze the robustness of regression or propensity score-matched treatment estimates to unobserved selection (endogeneity) bias. Based on the principles of the Heckman treatment model, the MBE entails estimating matched treatment effects within a range of propensity scores that minimizes unobserved selection bias. A major advantage of the MBE is that an instrumental variable is not required. The potential utility of the MBE in accounting studies is highlighted, and a familiar empirical illustration is provided

Prospect risk, pot odds and efficient drill or no-drill decision making: what the exploration business can learn from high stakes poker

A decision to proceed with risk ventures, such as exploration wells, requires three basic estimates: the cost, if the venture fails; the reward, if the venture succeeds; and the chance of success (risk). These three estimates are combined to derive the Expected Value and Expected Rate of Return, which are important inputs to go/no-go decisions. However, while cost and reward are seen as relatively “hard” numbers, based on measurable quantities and established price forecasts, risk is commonly seen as a “soft” number, an opinion based on incomplete knowledge. Decisions may be deferred, seeking more constraint on the risk estimate; this delay can be counterproductive. An alternative approach is used by professional poker players to make an equivalent decision. In that business, too, the chance of winning is harder to constrain than the cost and reward. Instead of seeking to fine-tune the risk, players compare a rough estimate of chance against “Pot Odds”, an easily-calculated number (the chance of winning needed to break even), and use this comparison to make the right decision efficiently. This approach can also be used in the exploration business. Pot Odds of a prospect can be calculated using expected dry hole costs and the predicted value of a discovery. comparison with the estimated chance of success may indicate whether we already have enough information to make the appropriate decision, or whether further work is justified. This may improve business decision making efficiency or provide a sense check on decisions already made

How do salt withdrawal minibasins form? Insights from forward modelling, and implications for hydrocarbon migration

Existing models for the initiation of salt withdrawal minibasins focus on the role of triggers that exist within the minibasin, either stratigraphic (e.g. differential deposition) or tectonic (extension, translation or contraction). Existing studies tend to focus on complex settings, such as continental margins, which contain many different potential triggering mechanisms. It can be difficult in these settings to identify which process is responsible for minibasin initiation, or the influence of individual factors on their subsequent development. Salt withdrawal minibasins also exist in simpler settings, without any obvious intrinsic trigger; the region of the North German Basin used by Trusheim (1960) in the classic definition of salt withdrawal geometries was of this nature. There is no overall basal or surface slope, no major lateral movement, and there is no depositional heterogeneity. Previously recognized trigger processes for minibasin initiation do not apply in this benign setting, suggesting that other, potentially more fundamental, influences may be at work. A simple forward-modelling approach shows how, in the absence of any other mechanism, a new minibasin can develop as the consequence of salt movement driven by its neighbour, and families of withdrawal minibasins can propagate across a region from a single seed point. This new mechanism may explain how some minibasins appear to initiate before the sediment density has exceeded that of the underlying salt. The forward modelling also indicates that some minibasins begin to invert to form turtle anticlines before the underlying salt has been evacuated, so that the timing of turtle formation may not be diagnostic of weld formation. This mechanism may also give rise to salt-cored turtles that have a lens of salt trapped beneath their cores. These new findings have implications for hydrocarbon migration and trapping

The engines of gravity-driven movement on passive margins: quantifying the relative contribution of spreading vs. gravity sliding mechanisms

Movement of gravity-driven systems on passive margins is fuelled by the loss of gravitational potential energy. Two end-member modes (gravity spreading and gravity gliding) are defined by whether the potential energy loss is due to deformation and movement towards the base of the system (spreading), or by movement parallel to the base of the system (gliding); most natural systems consist of a mixture of the two processes. Hitherto, use of these concepts has been limited or equivocal due to lack of a quantitative measure. In some cases, characterisation of gliding vs. spreading systems based on secondary attributes has resulted in controversy, because there is a lack of consensus as to which of these are truly diagnostic. This paper presents a new, simple quantitative method based on vector analysis, providing a numerical measure of the relative contribution of spreading vs. gliding. The method is applied to synthetic examples, where deformation can be tracked, and to natural examples where a valid palinspastic reconstruction is available. The results confirm that most natural examples exhibit mixed-mode behaviour, and that some have been mischaracterized; much of the Angola margin is dominated by spreading. The method can also provide an estimate of the absolute amount of gravitational potential energy released in the movement, and the energy contribution made by gliding vs. spreading. Determining the dominant process has implications for predicting the development of seafloor topography and stratal architecture

The impact of filing micro-entity accounts and the disclosure of reporting accountants on credit scores: an exploratory study

There is a dearth of evidence regarding the potential costs incurred by small private companies that opt to publish only an unaudited abbreviated balance sheet. This paper provides new evidence regarding whether UK companies that publish reduced balance sheet information in micro-entity annual accounts are allocated lower credit scores by a credit rating agency. Recently, for the smallest companies, a new exemption category for ‘micro-entities’ was introduced. Qualifying companies may elect to file even less unaudited balance sheet information than their small company counterparts. Consistent with the conjecture that publishing micro accounts conveys a negative signal to the credit scorer, there is systematic evidence that micro-entities are assigned worse credit scores. This result is robust to the employment of statistical methods that account for observed and unobserved bias. Based on both assurance and signalling tenets, the second novel conjecture examined in this study, is that companies which disclose their annual accounts are prepared by an accountancy firm (reporting accountant) will attract higher credit scores. Contrary to extant research which reports that companies that opt for voluntary audits receive higher credit scores, there is no evidence that the credit scorer rewards companies whose accounts bear the imprimatur of a reporting accountant

Compression failure of angle-ply laminates

The present work deals with modes and mechanisms of failure in compression of angle-ply laminates. Experimental results were obtained from 42 angle-ply IM7/8551-7a specimens with a lay-up of ((plus or minus theta)/(plus or minus theta)) sub 6s where theta, the off-axis angle, ranged from 0 degrees to 90 degrees. The results showed four failure modes, these modes being a function of off-axis angle. Failure modes include fiber compression, inplane transverse tension, inplane shear, and inplane transverse compression. Excessive interlaminar shear strain was also considered as an important mode of failure. At low off-axis angles, experimentally observed values were considerably lower than published strengths. It was determined that laminate imperfections in the form of layer waviness could be a major factor in reducing compression strength. Previously developed linear buckling and geometrically nonlinear theories were used, with modifications and enhancements, to examine the influence of layer waviness on compression response. The wavy layer is described by a wave amplitude and a wave length. Linear elastic stress-strain response is assumed. The geometrically nonlinear theory, in conjunction with the maximum stress failure criterion, was used to predict compression failure and failure modes for the angle-ply laminates. A range of wave length and amplitudes were used. It was found that for 0 less than or equal to theta less than or equal to 15 degrees failure was most likely due to fiber compression. For 15 degrees less than theta less than or equal to 35 degrees, failure was most likely due to inplane transverse tension. For 35 degrees less than theta less than or equal to 70 degrees, failure was most likely due to inplane shear. For theta less than 70 degrees, failure was most likely due to inplane transverse compression. The fiber compression and transverse tension failure modes depended more heavily on wave length than on wave amplitude. Thus using a single parameter, such as a ratio of wave amplitude to wave length, to describe waviness in a laminate would be inaccurate. Throughout, results for AS4/3502, studied previously, are included for comparison. At low off-axis angles, the AS4/3502 material system was found to be less sensitive to layer waviness than IM7/8551-7a. Analytical predictions were also obtained for laminates with waviness in only some of the layers. For this type of waviness, laminate compression strength could also be considered a function of which layers in the laminate were wavy, and where those wavy layers were. Overall, the geometrically nonlinear model correlates well with experimental results

The Significance of Culture for Development Studies

SUMMARY Though many arguments for the role of cultural factors in development have been circular or ideological, development is necessarily a culturally determined process. It is an attempt to realize certain aspirations which, however universal, are still held in the context of other goals particular to national or religious traditions which the subjects of development wish to preserve. Cultures also provide particular institutional means (sex roles, forms of organization, etc.) of development. As a precipitate of history, culture also includes people's ideas about the conditions of development itself. If we are seriously to engage with the subjects of development, these above all cannot be ignored. RESUME L'Impact de la Tradition Culturelle sur le Développement Si maintes arguments apportés a l'appui du rôle culturel dans le développement sont de nature péremptoire ou idéologique, le processus de développement reste essentiellement conditionné par la culture. Ce processus vise à la réalisation de certaines aspirations, si universelles qu'elles soient, qui demeurent toujours axées sur d'autres objectifs particuliers à la culture, nationale ou réligieuse que les intéressés en voie de développement tiennent à conserver. La culture inspire la forme des instruments institutionnels de développement (rôles sexuels, modèles d'organisation); sur le plan historique, elle représente les notions humaines sur la nature même du développement. Aucun chercheur sérieux, se consacrant à l'étude du développement ne peut se permettre d'ignorer ces considérations. RESUMEN La Importancia de la Cultura para los Estudios del Desarrollo Aunque es cierto que muchos de los argumentos relacionados con el rol de los factores culturales en el desarrollo han sido de carácter circular o ideológico, el desarrollo es por necesidad un proceso determinado culturalmente. Es un intento de llevar a cab o ciertas aspiraciones que, si bien son universales, están sin embargo envueltas en el contexto de otras metas, correspondientes a las tradiciones nacionales o religiosas que los sujetos del desarrollo desean preservar. Las diferentes culturas proveen además medios institucionales específicos para el desarrollo (rol de los sexos, formas de organización, etc. . . .). Como un precipitado de la historia, la cultura también incluye las ideas que la gente tiene acerca de las condiciones del desarrollo mismo. Si se trata de interesarse seriamente en los sujetos del desarrollo, éstos, por sobre todo, no pueden ser ignorados