Search results

The authors analyze a model for N different measurements of a persistent latent time series when measurement errors are mean-reverting, which implies a common trend among measurements. The authors study the consequences of overdifferencing, finding potentially large biases in maximum likelihood estimators (MLE) of the dynamics parameters and reductions in the precision of smoothed estimates of the latent variable, especially for multiperiod objects such as quinquennial growth rates. The authors also develop an R² measure of common trend observability that determines the severity of misspecification. Finally, the authors apply their framework to US quarterly data on GDE and GDI, obtaining an improved aggregate output measure.

Presents an adaptive slicing procedure for improving the geometric accuracy of layered manufacturing techniques which, unlike previous procedures, uses layers with sloping boundary surfaces that closely match the shape of the required surface. This greatly reduces the stair case effect which is characteristic of layered components with square edges. Considers two measures of error, and outlines a method of predicting these measures for sloping layer surfaces. To cater for different manufacturing requirements, presents a method to produce parts with either an inside or outside tolerance, or a combination of both. Finally, considers some problems associated with surface joins, vertices, and inflection points and proposes some solutions.

Indicators of financial crises generally do not have a good track record. This chapter presents an early warning system (EWS) for six countries in Asia in which indicators do work. We extract a full list of currency crisis indicators from the literature, apply factor analysis to combine the indicators, and use these factors as explanatory variables in logit models which are estimated for the period 1970:01–2001:12. The quality of the EWS is assessed both in-sample and out-of-sample. We find that money growth (M1 and M2), national savings, and import growth correlate with currency crises.

This article proposes a new approach to detecting the presence of common cyclical features when several time series are sampled at different frequencies. We generalize the common-frequency approach introduced by Engle and Kozicki (1993) and Vahid and Engle (1993). We start with the mixed-frequency VAR representation investigated in Ghysels (2012) for stationary time series. For non-stationary time series in levels, we show that one has to account for the presence of two sets of long-run relationships. The first set is implied by identities stemming from the fact that the differences of the high-frequency I (1) regressors are stationary. The second set comes from possible additional long-run relationships between one of the high-frequency series and the low-frequency variables. Our transformed vector error-correction model (VECM) representations extend the results of Ghysels (2012) and are important for determining the correct set of variables to be used in a subsequent common cycle investigation. This fact has implications for the distribution of test statistics and for forecasting. Empirical analyses with quarterly real gross national product (GNP) and monthly industrial production indices for, respectively, the United States and Germany illustrate our new approach. We also conduct a Monte Carlo study which compares our proposed mixed-frequency models with models stemming from classical temporal aggregation methods.

This paper describes a free‐piston driven expansion tube and its instrumentation. The facility is used to generate rarefied flows at speeds of approximately 10 km/s. Although the flow in the tube itself is in the continuum regime, rarefied flow conditions are achieved by allowing the test gas to further expand as a free jet into the facility's test section. The test flow is surveyed to provide bar‐gauge pressure measurements. Numerical simulation is then used to describe more fully the test flow properties. The flows produced are suitable for the aerodynamic testing of small models at superorbital speeds and should provide data that are suitable for the calibration of Direct Simulation Monte‐Carlo codes.

We propose a generic algorithm for numerically accurate likelihood evaluation of a broad class of spatial models characterized by a high-dimensional latent Gaussian process and non-Gaussian response variables. The class of models under consideration includes specifications for discrete choices, event counts and limited-dependent variables (truncation, censoring, and sample selection) among others. Our algorithm relies upon a novel implementation of efficient importance sampling (EIS) specifically designed to exploit typical sparsity of high-dimensional spatial precision (or covariance) matrices. It is numerically very accurate and computationally feasible even for very high-dimensional latent processes. Thus, maximum likelihood (ML) estimation of high-dimensional non-Gaussian spatial models, hitherto considered to be computationally prohibitive, becomes feasible. We illustrate our approach with ML estimation of a spatial probit for US presidential voting decisions and spatial count data models (Poisson and Negbin) for firm location choices.

This paper examines the association of charitable donations with quality of care proxies for nonprofit hospice providers in the United States (US). An estimated 1.45 million patients received hospice care in the US in 2008. Medicare hospice spending exceeded $10 billion in 2007 and is expected to more than double over the next 10 years. Using Guidestar and Medicare Hospice Cost Report data, we find donations are positively associated with proxies for nurse and social worker quality of care, but not with our home-health aide quality proxy. This research adds to our understanding of charitable contributions in hospice provider organizations.

TruSurf is a new system for building solid objects from layers with sloping surfaces that closely match the designed surface shape. The advantages of using sloping surfaces over stepped edges are improved surface finish, and decreased build time through the use of thicker layers. TruSurf uses B‐spline surfaces to describe the part, and calculate the sloped path of the layer cutting medium. Describes operation of the system in detail and presents results from the production of some test parts. Discusses some ways for improving accuracy, including using principal directions of minimum surface curvature, and using a curved cutting medium to produce layers.

This study aims to expand the conventional tax effort model to incorporate relevant economic freedom variables to investigate whether economic freedom fosters tax revenue performance in `sub-Saharan Africa (SSA).

This study uses data from 42 countries across the four sub-regions of SSA from the period 2005 to 2012 with 252 year-country observations in an unbalanced panel method. The data were statistically treated using feasible generalised least square (FGLS) and panel-corrected standard errors (PCSE) estimate techniques.

The findings are twofold. First, the principal finding of the study suggests that economic freedom promotes tax revenue performance. Precisely, the FGLS analysis indicates that property rights freedom, freedom from corruption and investment freedom, as well as the composite economic freedom, exerted positive significant impact on tax revenue performance. This implies that country, which attained high degree of economic freedom, is likely to have higher tax-to-GDP ratio than a country with low level of economic freedom. Secondly, the results of most conventional variables conform to the prediction in the traditional theory except per capita income. Specifically, agriculture share in GDP and per capita income indicate negative significant relationship with tax revenue performance.

Because little is known empirically about the connection between economic freedom and tax revenue performance, this study extended the conventional tax effort model to incorporate the economic freedom to bridge the knowledge gap due to the absence of empirical evidence on the relationship between economic freedom and tax effort.