bluuebunny/crossref_metadata_2025 huggingface dataset:
Ethical Issues in Technology Assessment:Conceptual Categories and Procedural Considerations
Authors: Heitman Elizabeth
Published: March 2009

The practice of health care technology assessment involves ethical considerations in all of its varied functions and techniques. Ethical issues in technology assessment can be grouped into the broad categories of normative concepts, diagnosis, prevention and therapy, research and the advancement of knowledge, and allocation of resources. Moreover, the ethics of the assessment process itself must be evaluated in terms of the integrity of the project's goals, procedures, and effects, and evaluators’ open and self-critical acknowledgment of their purposes. As a relatively new field, technology assessment can benefit from using a variety of analytic approaches as it works to develop its own methods for evaluating ethical issues related to technology.
Technology and the Doctor-Patient Relationship
Authors: King R. C.
Published: March 2009

It was in 1967 that the first patient went from Tunbridge Wells to the Brompton Hospital for pacemaker implantation. The recipient was a typically robust female octogenarian and while the eminent cardiologist was engaged in his task, she tapped him on the shoulder. “Young man” she said, “how many of these operations have you done?” He replied, somewhat modestly, “About 300,” expecting her to compliment him on his expertise. Instead, she said “Well, if you've done that many you should know to keep your patient's feet warm. Cover them up!” This anecdote aptly illustrates the contention implied in my title that a new and somewhat disruptive dimension in the form of technology has entered the field of medicine, a view which has attracted considerable support from various quarters (14; 16).
Technology and the Undergraduate Medical Curriculum
Authors: Barondess Jeremiah A.
Published: March 2009

Instruction of medical students in the use of technologic procedures in clinical medicine has emerged in recent years on a more or less piecemeal basis. Individual technologies are introduced as the teaching hospital acquires the requisite equipment and personnel; as experience is gained by faculty and attending staff some sense emerges of the indications, contraindications, risks, accuracy, and usefulness of a procedure, which then is transmitted to housestaff and students. Instruction is likely to occur on a case-by-case basis, supplemented occasionally by conferences or formal presentations, generally oriented around major innovations, such as computerized transaxial tomography or magnetic resonance imaging. As relevant clinical literature appears, it is used to reiterate and expand the available information base of trainees, but to a considerably greater extent for housestaff than for students. Ultimately what emerges is a pattern of use, a gestalt, for each technology, reflecting the synthesis of the available information and clinical experience with the procedure in the particular institution. In view of the enormous number and variety of technologies available, the task of the student or house officer in acquiring even basic familiarity with those in common use is formidable. A coherent approach to instruction in the use of technologic procedures is required. Students need, and medical faculties must find, a way to provide intellectual systems for incorporating technologies into the clinical armamentarium in a manner that permits them to be maximally useful.
Impact of Technology on the Education of Health Care Professionals
Authors: Laidlaw Jennifer M. , Harden R. M.
Published: March 2009

A rapid development in health care delivery has been the increasing use of technology. Technology will continue to transform medical practice and all health care workers are involved with technology by accident or design. This has resulted in technology dominating many health policy decisions (4).
Which are the Best Information Sources for Identifying Emerging Health Care Technologies?: An International Delphi Survey
Authors: Robert Glenn , Gabbay John , Stevens Andrew
Published: March 2009

The purpose of this survey was to assess potential information sources for identifying new health care technologies. A three-round Delphi study was conducted, involving 38 selected experts who suggested and assessed potential sources by applying agreed criteria. Twenty-six potential information sources were considered. Timeliness, time efficiency, and sensitivity were important criteria in determining which were the most important sources. The eight recommended sources were: pharmaceutical journals, pharmaceutical and biotechnology companies, specialist medical journals, key medical journals, medical engineering companies, private health care providers, newsletters and bulletins from other health technology assessment agencies, and groups of expert health professionals. There is a need to use a combination of sources because the most useful sources will vary according to the type of technology under consideration.
The Early Experiences of a National System for the Identification and Assessment of Emerging Health Care Technologies in Sweden
Authors: Carlsson Per , Hultin Henric , Törnwall Johanna
Published: March 2009

This article presents the experiences from a pilot study and the establishment of a permanent system called SBU Alert. The question of establishing a system for the identification and assessment of emerging technologies in health care in Sweden has been on the agenda since the late 1980s. The demand came primarily from policy makers. The pilot study showed that the awareness of the project in the target group (politicians, leading managers, hospital directors, and senior medical advisors) was high. Almost all of those who replied to an assessment questionnaire were in favor of a continuation of the work. In 1997, the Swedish Council on Technology Assessment in Health Care (SBU) was selected to establish a permanent organization. This work has resulted in the identification of a number of methodological problems and tentative solutions concerning all components in the SBU Alert system. We have found that a system for systematic identification and early assessment of emerging technologies is a new and promising tool in the health technology assessment arsenal. Still, experiences are limited. Methodology and the impact of early judgments on decision making need further evaluation.
Cost-Utility Analysis of Total Hip Arthroplasties: Technology Assessment of Surgical Procedures by Mailed Questionnaires
Authors: Givon Uri , Ginsberg Gary M. , Horoszowski Henri , Shemer Joshua
Published: March 2009

A retrospective study comparing 700 consecutive total hip arthroplasties, utilizing four types of implants, was performed. Questionnaires based on hip scores were sent to 593 living patients. Useful responses were received from 363 (61 %) patients. Hip scores and quality-adjusted life-years were calculated. Multiple regression analysis, controlling for all possible biases, demonstrated one cementless implant as superior to all others. We believe that the use of mailed questionnaires is a simple and convenient system of follow-up, saving patients the need for outpatient clinic visits. The validity of such replies, however, has yet to be established.
Econometric Analysis of Variation in Cesarean Section Rates: A Cross-sectional Study of 59 Obstetrical Departments in Sweden
Authors: Eckerlund Ingemar , Gerdtham Ulf-G
Published: March 2009

The objective of this study was to explain the variation in cesarean section rates among hospitals (obstetrical departments) in Sweden, and to discuss its potential economic consequences. Using data from The Swedish Medical Birth Registry 1991, we made a cross-sectional study of the cesarean section rate at the departmental level. We identified some 20 determinants, demand-related as well as supply-related. A general model including all these regressors was specified. After reducing this model, we were able to explain about one-quarter of the variation. We conclude that the large variation in cesarean section rates indicates inefficiency, due mainly to overutilization, but perhaps also underutilization. It is difficult to calculate the economic consequences or the welfare loss to society. We estimated an additional cost for unnecessary cesarean sections of 13—16 million Swedish crowns (SEK) per year.
A Clinical and Economic Evaluation of Red Blood Cell Transfusions in Patients Receiving Cancer Chemotherapy
Authors: Ortega Ana , Dranitsaris George , Puodziunas Anitasha
Published: March 2009

A clinical and economic evaluation of red blood cell (RBC) utilization in cancer patients during chemotherapy is described. Using a randomized sampling process, 100 patients who had received chemotherapy with or without cisplatin were selected (50 in each group). Multiple logistic regression was then used to identify risks factors for transfusion requirements. Twenty-five percent of patients in the cisplatin and 12% in the noncisplatin group received at least one blood transfusion during chemotherapy (p=.09). Depressed hemoglobin levels and cisplatin dosage were identified as risk factors for transfusion requirements. Combining all transfused patients revealed an overall cost of Can $599 (95% Cl: $513–$683) per transfusion. The results of the current study indicated that anemia is a common complication of cancer chemotherapy that can be costly to manage.
Evidence-Informed Patient Choice: Practical Issues of Involving Patients in Decisions About Health Care Technologies
Authors: Entwistle Vikki A. , Sheldon Trevor A. , Sowden Amanda , Watt Ian S.
Published: March 2009

Evidence-informed patient choice involves providing people with research-based information about the effectiveness of health care options and promoting their involvement in decisions about their treatment. Although the concept seems desirable, the processes and outcomes of evidence-informed patient choice are poorly understood, and it should be carefully evaluated.
Estimating the Costs of Hip Fracture and Potential Savings
Authors: Zethraeus Niklas , Gerdtham Ulf-G
Published: March 2009

This paper examines the determinants of hip fracture costs and further evaluates potential savings in costs when the occurrence of hip fracture is prevented. The costs of hip fracture are comprised of direct costs from health care and the social welfare system. Data were collected for 1,080 postmenopausal women admitted from private residence for primary hip fracture surgery during the year of 1992 in the city of Stockholm, Sweden. It was found that the cost of hip fracture is significantly related to age, mortality the year after a fracture, type of fracture, costs 1 year before a fracture, and hospital admission. The savings in direct costs for an average woman surviving the year after a fracture amount to SEK 210,000.
Health State Preferences of Persons with Anxiety
Authors: Patrick Donald L. , Mathias Susan D. , Elkin Eric P. , Fifer Sheila K. , Buesching Don P.
Published: March 2009

We compared patient ratings of the desirability of anxiety health states with measures of psychological distress and functional status and investigated how these ratings predicted treatment by primary care and mental health clinicians. As expected, associations between desirability ratings and psychological and physical health status were low to moderate. Persons who rated their current anxiety health state as more desirable received fewer mental health referrals and were statistically more likely to receive a prescription for psychotropic medication. Simple ratings of health state desirability may help clinicians evaluate patients' views of their health status and discuss potential treatment options.
When Is the ‘right’ Time to Initiate an Assessment of a Health Technology
Authors: Mowatt Graham , Bower D. Jane , Brebner John A. , Cairns John A. , Grant Adrian M. , Mckee Lorna
Published: March 2009

There is currently no generally accepted formula for the optimal timing of health technology assessments (HTAs). This paper presents some of the relevant issues and then reviews the existing literature on timing of HTAs. It finds that the literature that specifically addresses these issues is limited. There is a consensus that HTAs should be initiated at an early stage of the development of a new health technology, and repeated during the life cycle of the technology. However, the questions of reliably identifying new technologies at an early stage in their development and of deciding on a detectable critical point for starting evaluation are not resolved. It is proposed that a system of categorization and prioritization of health technologies should be developed to allow decisions to be made as to when a strongly precautionary approach is required and how the limited resources available for HTA could be optimally deployed.
Extracorporeal Membrane Oxygenation
Authors: Lister George
Published: March 2009

Extracorporeal membrane oxygenation (ECMO) is a means of diverting a fraction or all of the circulation through a device that permits gas exchange across a permeable membrane. The site of removal and the site of return of blood are dictated primarily by practical considerations based on the volume of flow of blood to be diverted and whether a particular organ is to be bypassed. The prototype of extracorporeal oxygenation is heart-lung bypass, used for various types of cardiac surgery, in which the entire venous return is diverted through an oxygenator (bubble or membrane type) and returned to the aorta. Since the earliest reports of the use of ECMO in neonates, venoarterial bypass has been the preferred route, with blood drained from the right atrium and returned either to the carotid artery or to the femoral artery, although the former seems to have been used most often (2;4;11;12;14;18). In some reports, veno-venous bypass has also been accomplished with removal of blood from the right atrium and return into the umbilical or femoral vein (13;19). Gas exchange across the lung may also continue, although the ventilator rate, tidal volume, or peak inspiratory pressure are usually reduced markedly during the period of extracorporeal oxygenation. Anticoagulation is accomplished with few problems by infusion of heparin sulfate throughout the duration of the procedure. There now have been enough reports in the literature (individual cases or series of patients) to demonstrate that the procedure can be carried out with a minimum of technical difficulties in newborn infants (2;3;4;11;12;18), although the selection of “appropriate” patients reduces the morbidity and technical challenges of the procedure.
Electrolyte Balance
Authors: Aperia Anita , Herin Peter
Published: March 2009

The kidney is structurally and biochemically immature at birth. As a consequence, renal function is low (3;10;ll;18). Glomerular filtration rate (related to body surface area or to body weight) is approximately 25% of that in adults. The capacity of several different tubular transport systems is lower in the infant than in the adult (2;5;13;21;28). A low transporting capacity of the neonatal kidney will sometimes result in undesired losses of electrolytes, amino acids, and peptides. The capacity to concentrate urine is low (7;29), and disturbances of serum tonicity, therefore, are common. The low concentrating capacity can be attributed to renal immaturity. The capacity of the newborn fullterm as well as preterm infant to release antidiuretic hormone is normal 7;31).
Nutritional Needs of Newborn Infants in Intensive Care
Authors: Okken Albert
Published: March 2009

In a review of the literature concerning the nutritional needs of newborn infants in intensive care, one surprisingly finds that only a few studies on this subject have been performed. This is in contrast to the extensive literature regarding the nutritional needs of healthy, growing newborn infants. It is astonishing, further, to find that there are many reports on the metabolic effects of illness in adults but hardly any on those in children and newborn infants. In fact, in a recent textbook of pediatric intensive care, in the chapter on nutrition and metabolism in the critically ill child, the authors state, “the metabolic derangements that occur in children have not been well delineated during critical illness, so that data and findings discussed have been taken mostly from the adult literature.”
Which Neurological Examinations can be used to Predict Outcome During the Neonatal Period?
Authors: Cowan Frances
Published: March 2009

In this review I shall discuss the prognostic value of the clinical neurological examination, the EEG (and the various methods of recording it), evoked responses, and Doppler ultrasound measurements of cerebral blood velocity. Imaging modalities (ultrasound, CT, MRI) will be dealt with elsewhere under discussion of their diagnostic value.
Neurological and Developmental Follow-Up of a Population at Risk
Authors: Stewart Ann L.
Published: March 2009

Neurodevelopmental follow-up has an important role in perinatal management and research. The value of individual studies depends on the quality of the planning, the data collected, and the interpretation of the findings. Interpretation, in particular, has caused many problems; these have usually arisen because of a failure to understand the nature of the data and what they mean. Follow-up studies are labor intensive and, therefore, very expensive. If they are to continue, there must be a full understanding of their strengths and weaknesses by those who plan them, carry them out, and — above all, by those who analyze and interpret them.
Moral Dilemmas in Neonatal Medicine
Authors: Saugstad Ola Didrik
Published: March 2009

Modern neonatal medicine raises a series of fundamental ethical questions. In the confrontation with these and in attempting to solve them, basic concepts concerning human life and death should be discussed. On what values do we base our practice? Terms such as human, right to life, sanctity of life, equality, and justice should all be considered with reference to the sick newborn baby. Leading Anglo-American contemporary philosophers who deal with such concepts have a tendency to link them to the autonomy of the individual. Is this a fruitful approach when dealing with ethical questions in neonatal medicine? In the following, I will exemplify this to elucidate the problem.
Ethical Problems in Neonatal Intensive Care
Authors: Raivio Kari O.
Published: March 2009

Treatment decisions in the delivery room and neonatal intensive care unit are often life-and-death decisions. In a true Hippocratic spirit of “do no harm,” the guiding principle should be the long-term outlook for the infant and the family. This is usually, but not always, determined by the prospects of normal or near normal mental development versus incapacitating injury.
Competence and Compliance in Antenatal Care: Experience from Sweden
Authors: Åberg Anders , Lindmark Gunilla
Published: March 2009

Swedish antenatal care is staffed by midwives working within the primary health care system, but with close collaboration with the hospital. The compliance to the program both from staff and mothers is very high, with 13.2 visits on average. There is a regional variation both in the number of visits and in the use of routine tests.
Antenatal Care in Denmark: Assessments of Program, Staff Competence, Compliance, and Outcome
Authors: Kristensen Finn Børlum
Published: March 2009

Antenatal care in Denmark is shared between general practitioners, midwives, and hospital departments. A minimum of 9 visits is officially recommended for all pregnant women. In 1987, 80% made 10 or more visits. An inadequate number of visits in relation to recommendations was most frequent in the lowest social group. Risk of stillbirth and neonatal death varied substantially between social groups even after taking account of number of visits made.
Diagnostic and Preventive Possibilities of Excessive Drinking in Antenatal Care
Authors: Larsson Gunilla
Published: March 2009

Alcoholism among women has increased during the last decades. Thus it is likely that an increasing number of pregnancies will involve risk of alcohol damage to the fetus. In this article, two antenatal programs are presented to identify pregnancies at risk. Adequate alcohol information seems to be sufficient for socially drinking women, whereas alcoholic women need extensive support to abstain from alcohol. The psychosocial support was not experienced as intrusive.
Perspectives of Users of the Services
Authors: Oakley Ann
Published: March 2009

This article draws on social science evidence concerning the views and experiences of those using the antenatal services. It identifies several important themes in this evidence, including the need to consider pregnancy a normal process, to provide care that is sensitive to individual circumstances and that offers continuity of care throughout the antenatal period, and the obligation on providers to assess scientifically the effectiveness of the care they give.
Antenatal Diagnosis of Intrauterine Growth Retardation by Ultrasound
Authors: Maršál Karel
Published: March 2009

Ultrasound estimation of fetal weight or ultrasound measurement of fetal abdomen alone enables identification of small-for-gestational-age fetuses. A prerequisite for this is a reliable dating of pregnancy, which is provided by a routine ultrasound screening in the first half of gestation. The fetal growth can be followed by serial fetometric measurements. As a standard, charts of intrauterine growth based on the ultrasonic measurement can be used. As a secondary diagnostic test for monitoring fetal health in pregnancies suspected of intrauterine growth retardation, Doppler ultrasound evaluation of fetal and uteroplacental hemodynamics provided useful for early detection of imminent fetal distress.
Classes of Similar Regions and Their Power Properties for Some Econometric Testing Problems
Authors: Hillier Grant H.
Published: March 2009

In an hypothesis testing problem involving nuisance parameters for which boundedly complete sufficient statistics exist under the null hypothesis, the class of all similar regions for the problem is characterized by the conditional distribution of the data given these sufficient statistics. If there exists a one-to-one transformationy→ (t, u) of the data,y, to the sufficient statistic,t, and a second vector of statistics,u, that is independent oftunder the null hypothesis, then the statisticuitself characterizes the class of similar regions. This paper applies this idea to five testing problems of interest in econometrics. In each case we obtain the density of the relevant statistic under the null hypothesis, when it is free of nuisance parameters, and under the alternative. Using the density under the alternative, we discuss the power properties of the class of similar tests for each problem. Other applications are also suggested.
Asymptotic Expansions in Nonstationary Vector Autoregressions
Authors: Phillips P. C. B.
Published: March 2009

This paper studies the statistical properties of vector autoregressions (VAR's) for quite general multiple time series which are integrated processes of order one. Functional central limit theorems are given for multivariate partial sums of weakly dependent innovations and these are applied to yield first-order asymptotics in nonstationary VAR's. Characteristic and cumulant functionals for generalized random processes are introduced as a means of developing a refinement of central limit theory on function spaces. The theory is used to find asymptotic expansions of the regression coefficients in nonstationary VAR's under very general conditions. The results are specialized to the scalar case and are related to other recent work by the author [21].
Global and Partial Non-Nested Hypotheses and Asymptotic Local Power
Authors: Pesaran M. Hashem
Published: March 2009

This paper addresses two related issues in the literature of non-nested hypotheses testing. Firstly, by means of a measure of “closeness” of probability density functions, it shows howanytwo hypotheses can be placed into the nested and the non-nested categories with the latter category being subdivided further into “globally” and “partially” non-nested hypotheses. Secondly, by emphasizing the distinction between a “local null” and a “local alternative,” the paper shows that only in the case of partially non-nested hypotheses is it possible to specify local alternatives. In this case the paper derives the asymptotic distribution of the Cox test statistic under local alternatives and shows that it is distributed as a normal variate with a mean which is directly related to the measure of “closeness” of the alternative to the null hypothesis.
Least Squares Regression with Integrated or Dynamic Regressors under Weak Error Assumptions
Authors: Andrews Donald W. K.
Published: March 2009

This paper establishes consistency of least squares estimators in (i) a multiple regression model with integrated regressors and explosive, non-mixing errors, and (ii) a dynamic linear regression model with regressors and errors that may have infinite variances. In the former context, the asymptotic distribution of the least squares estimator also is obtained, in certain cases.
The ET Interview: Professor J. Tinbergen
Authors: Magnus Jan R. , Morgan Mary S.
Published: March 2009

Jan Tinbergen is one of the founding fathers of econometrics, publishing in the field from 1927 until the early 1950s. This was the frontier age of econometrics when the distinction between mathematical economics and econometrics, let alone between theoretical and applied econometrics, did not yet exist. Tinbergen's approach to economics has always been a practical one. This was highly appropriate for the new field of econometrics, and enabled him to make important contributions to conceptual and theoretical issues, but always in the context of a relevant economic problem. The development of the first macroeconometric models, the solution of the identification problem, and the understanding of dynamic models are perhaps his three most important legacies to econometrics. Tinbergen was awarded the first Nobel Memorial Prize in economics in 1969 (jointly with Ragnar Frisch) for his contributions to econometrics.

Tinbergen's desire to communicate his ideas to others is matched by a talent for clear and direct writing. This gives his econometric work great appeal and an apparent simplicity which should not be underestimated. This talent was also fruitfully applied to the development of pedagogical tools for teaching econometrics to his students.

Since the early 1950s Tinbergen's interests have moved on and he has made notable contributions to such diverse fields as the theory of economic policy, development planning, and income distribution. Tinbergen's political and pacifist views have always been an important element in his economics, and even, as this interview shows, his econometrics. His overriding aim has been to improve the welfare of the less fortunate in this world.

It is now 60 years since Tinbergen's first article in economics appeared, yet he shows no signs of retiring. We met him on May 27, 1986, in the study of his house in The Hague, where he has lived for most of his working life and which bears the hallmarks of continued study and writing. Most of the discussion during the afternoon concerned his econometric work published in the 1930s and 1940s. He gave us his views of those early developments—both what he thought then and how he sees them now. What follows is an edited transcript of the conversation. We hope that this interview will bring alive to the readers of the 1980s the issues and difficulties faced by econometricians in the 1930s, as well as Tinbergen's characteristic response to those problems. One of Tinbergen's attributes is a considerable modesty about his own achievements; the reader should bear this in mind when reading his remarks.
Asymptotically Efficient Estimation of Cointegration Regressions
Authors: Saikkonen Pentti
Published: March 2009

An asymptotic optimality theory for the estimation of cointegration regressions is developed in this paper. The theory applies to a reasonably wide class of estimators without making any specific assumptions about the probability distribution or short-run dynamics of the data-generating process. Due to the nonstandard nature of the estimation problem, the conventional minimum variance criterion does not provide a convenient measure of asymptotic efficiency. An alternative criterion, based on the concentration or peakedness of the limiting distribution of an estimator, is therefore adopted. The limiting distribution of estimators with maximum asymptotic efficiency is characterized in the paper and used to discuss the optimality of some known estimators. A new asymptotically efficient estimator is also introduced. This estimator is obtained from the ordinary least-squares estimator by a time domain correction which is nonparametric in the sense that no assumption of a finite parameter model is required. The estimator can be computed with least squares without any initial estimations.
Estimating Nonlinear Dynamic Models Using Least Absolute Error Estimation
Authors: Weiss Andrew A.
Published: March 2009

We consider least absolute error estimation in a dynamic nonlinear model with neither independent nor identically distributed errors. The estimator is shown to be consistent and asymptotically normal, with asymptotic covariance matrix depending on the errors through the heights of their density functions at their medians (zero). A consistent estimator of the asymptotic covariance matrix of the estimator is given, and the Wald, Lagrange multiplier, and likelihood ratio tests for linear restrictions on the parameters are discussed. A Lagrange multiplier test for heteroscedasticity based upon the absolute residuals is analyzed. This will be useful whenever the heights of the density functions are related to the dispersions.
Effects of Model Selection on Inference
Authors: Pötscher B.M.
Published: March 2009

The asymptotic properties of parameter estimators which are based on a model that has been selected by a model selection procedure are investigated. In particular, the asymptotic distribution is derived and the effects of the model selection process on subsequent inference are illustrated.
Asymptotics for Least Absolute Deviation Regression Estimators
Authors: Pollard David
Published: March 2009

The LAD estimator of the vector parameter in a linear regression is defined by minimizing the sum of the absolute values of the residuals. This paper provides a direct proof of asymptotic normality for the LAD estimator. The main theorem assumes deterministic carriers. The extension to random carriers includes the case of autoregressions whose error terms have finite second moments. For a first-order autoregression with Cauchy errors the LAD estimator is shown to converge at a 1/n rate.
Limit Theory for M-Estimates in an Integrated Infinite Variance
Authors: Knight Keith
Published: March 2009

We consider the limiting distributions of M-estimates of an “autoregressive” parameter when the observations come from an integrated linear process with infinite variance innovations. It is shown that M-estimates are, asymptotically, infinitely more efficient than the least-squares estimator (in the sense that they have a faster rate of convergence) and are conditionally asymptotically normal.
Strong Laws for Dependent Heterogeneous Processes
Authors: Hansen Bruce E.
Published: March 2009

This paper presents maximal inequalities and strong law of large numbers for weakly dependent heterogeneous random variables. Specifically considered are Lr mixingales for r > 1, strong mixing sequences, and near epoch dependent (NED) sequences. We provide the first strong law for Lr-bounded Lr mixingales and NED sequences for 1 > r > 2. The strong laws presented for α-mixing sequences are less restrictive than the laws of McLeish [8].
Who Invented Local Power Analysis?
Authors: McManus Douglas A.
Published: March 2009

Asymptotic local power analysis has become an important and increasingly used technique in econometrics. This paper reviews the history of local power analysis and delineates the contribution of J.Neyman, E.J.G. Pitman, and G. Noether.
On Limited Dependent Variable Models: Maximum Likelihood Estimation and Test of One-sided Hypothesis
Authors: Silvapulle Mervyn J.
Published: March 2009

The limited dependent variable models with errors having log-concave density functions are studied here. For such models with normal errors, the asymptotic normality of the maximum likelihood estimator was established by Amemiya [1]. We show, when the density of the error distribution is log-concave, that the maximum likelihood estimator exists with arbitrarily large probability for large sample sizes, and is asymptotically normal. The general theory presented here includes the important special cases of normal, logistic, and extreme value error distributions. The main results are established under rather weak conditions. It is also shown that, under the null hypothesis, the asymptotic distribution of the likelihood ratio statistic for testing a one-sided alternative hypothesis is a weighted sum of chi-squares.
A Shortcut to LAD Estimator Asymptotics
Authors: Phillips P.C.B.
Published: March 2009

Using generalized functions of random variables and generalized Taylor series expansions, we provide quick demonstrations of the asymptotic theory for the LAD estimator in a regression model setting. The approach is justified by the smoothing that is delivered in the limit by the asymptotics, whereby the generalized functions are forced to appear as linear functionals wherein they become real valued. Models with fixed and random regressors, and autoregressions with infinite variance errors are studied. Some new analytic results are obtained including an asymptotic expansion of the distribution of the LAD estimator.
A Unified Approach to Robust, Regression-Based Specification Tests
Authors: Wooldridge Jeffrey M.
Published: March 2009

This paper develops a general approach to robust, regression-based specification tests for (possibly) dynamic econometric models. A useful feature of the proposed tests is that, in addition to estimation under the null hypothesis, computation requires only a matrix linear least-squares regression and then an ordinary least-squares regression similar to those employed in popular nonrobust tests. For the leading cases of conditional mean and/or conditional variance tests, the proposed statistics are robust to departures from distributional assumptions that are not being tested, while maintaining asymptotic efficiency under ideal conditions. Moreover, the statistics can be computed using any √T-consistent estimator, resulting in significant simplifications in some otherwise difficult contexts. Among the examples covered are conditional mean tests for models estimated by weighted nonlinear least squares under misspecification of the conditional variance, tests of jointly parameterized conditional means and variances estimated by quasi-maximum likelihood under nonnormality, and some robust specification tests for a dynamic linear model estimated by two-stage least squares.
On the Sensitivity of a Regression Coefficient to Monotonic Transformations
Authors: Yitzhaki Shlomo
Published: March 2009

This note presents a procedure which enables the user to check whether a monotonic transformation can change the sign of a regression coefficient. One possible use of this procedure is to examine the robustness of key regression coefficients.
Stationarity and Persistence in the GARCH(1,1) Model
Authors: Nelson Daniel B.
Published: March 2009

This paper establishes necessary and sufficient conditions for the stationarity and ergodicity of the GARCH(l.l) process. As a special case, it is shown that the IGARCH(1,1) process with no drift converges almost surely to zero, while IGARCH(1,1) with a positive drift is strictly stationary and ergodic. We examine the persistence of shocks to conditional variance in the GARCH(l.l) model, and show that whether these shocks "persist" or not depends crucially on the definition of persistence. We also develop necessary and sufficient conditions for the finiteness of absolute moments of any (including fractional) order.
Functional Forms of Characteristic Functions and Characterizations of Multivariate Distributions
Authors: Chikuse Yasuko
Published: March 2009

During the Oxford Conference of the Econometric Society in 1936, Ragnar Frisch proposed a problem of characterization of distributions based on the property of linear regression of one linear function of random variables on the other. This problem has been solved, partially by Allen [1], and then completely by Rao [24,25], Fix [7], and Laha [13] relaxing the conditions imposed on the component random variables. The purpose of this paper is to solve the above mentioned problem for the multivariate case, characterizing multivariate distributions based on the multivariate linear regression of one linear function of not necessarily i.i.d. random vectors with matrix coefficients on the other. We make some mild assumptions concerning the component random vectors and the related constant matrices. It is shown that the property of multivariate linear regression yields a system of partial differential equations (p.d.e.'s) satisfied by the characteristic functions of the component random vectors. A general solution of this system of p.d.e.'s is given by certain functional forms. Special cases of the general solution give characterizations of the “multivariate generalized stable laws” and the multivariate semistable laws, and a method is presented to characterize the multivariate stable laws.
Additive Interactive Regression Models: Circumvention of the Curse of Dimensionality
Authors: Andrews Donald W.K. , Whang Yoon-Jae
Published: March 2009

This paper considers series estimators of additive interactive regression (AIR) models. AIR models are nonparametric regression models that generalize additive regression models by allowing interactions between different regressor variables. They place more restrictions on the regression function, however, than do fully nonparametric regression models. By doing so, they attempt to circumvent the curse of dimensionality that afflicts the estimation of fully non-parametric regression models.

In this paper, we present a finite sample bound and asymptotic rate of convergence results for the mean average squared error of series estimators that show that AIR models do circumvent the curse of dimensionality. A lower bound on the rate of convergence of these estimators is shown to depend on the order of the AIR model and the smoothness of the regression function, but not on the dimension of the regressor vector. Series estimators with fixed and data-dependent truncation parameters are considered.
Semiparametric Estimation of a Single-Index Model with Nonparametrically Generated Regressors
Authors: Ahn Hyungtaik
Published: March 2009

This paper develops a theory of estimating parameters of a generated regressor model in which some explanatory variables in the equation of interest are the unknown conditional means of certain observable variables given other observable regressors. The paper imposes a weak nonparametric restriction on the form of the conditional means and maintains a single-index assumption on the distribution of the dependent variable in the equation of interest. The estimation method follows a two-step approach: The first step estimates the conditional means in the index nonparametrically, and the second step estimates the parameters by an analytically convenient weighted average derivative method. It is established that the two-step estimator is root-n-consistent and asymptotically normal. The asymptotic variance exceeds that of the one-step hypothetical estimator, which would be obtainable if the first-step regression were known.
The Cumulant Generating Function Estimation Method
Authors: Knight John L. , Satchell Stephen E.
Published: March 2009

This paper deals with the use of the empirical cumulant generating function to consistently estimate the parameters of a distribution from data that are independent and identically distributed (i.i.d.). The technique is particularly suited to situations where the density function is unknown or unbounded in parameter space. We prove asymptotic equivalence of our technique to that of the empirical characteristic function and outline a six-step procedure for its implementation. Extensions of the approach to non-i.i.d. situations are considered along with a discussion of suitable applications and a worked example.
Additive Nonlinear ARX Time Series and Projection Estimates
Authors: Masry Elias , Tjøstheim Dag
Published: March 2009

We propose projections as means of identifying and estimating the components (endogenous and exogenous) of an additive nonlinear ARX model. The estimates are nonparametric in nature and involve averaging of kernel-type estimates. Such estimates have recently been treated informally in a univariate time series situation. Here we extend the scope to nonlinear ARX models and present a rigorous theory, including the derivation of asymptotic normality for the projection estimates under a precise set of regularity conditions.
Estimating Multiple Breaks One at a Time
Authors: Bai Jushan
Published: March 2009

Sequential (one-by-one) rather than simultaneous estimation of multiple breaks is investigated in this paper. The advantage of this method lies in its computational savings and its robustness to misspecification in the number of breaks. The number of least-squares regressions required to compute all of the break points is of order T, the sample size. Each estimated break point is shown to be consistent for one of the true ones despite underspecification of the number of breaks. More interestingly and somewhat surprisingly, the estimated break points are shown to be T-consistent, the same rate as the simultaneous estimation. Limiting distributions are also derived. Unlike simultaneous estimation, the limiting distributions are generally not symmetric and are influenced by regression parameters of all regimes. A simple method is introduced to obtain break point estimators that have the same limiting distributions as those obtained via simultaneous estimation. Finally, a procedure is proposed to consistently estimate the number of breaks.
Comparison of Deterministic and Stochastic Predictors in Nonlinear Systems When the Disturbances Are Small
Authors: Arvin-Rad Hassan
Published: March 2009

This paper compares the deterministic and stochastic predictors of nonlinear models when the disturbances are small. Large-sample properties of these predictors have been analyzed extensively in the econometric literature. While the deterministic predictors are asymptotically biased, there are some Monte Carlo experiments that suggest the magnitude of this bias is rather insignificant. Here, we offer a possible explanation of the smallness of the deterministic bias. It is shown that when the error terms have small standard deviation, the deterministic predictor turns out to be asymptotically unbiased. The results are based on deriving asymptotic expansions for alternative predictors. The asymptotic expansions carried out here are similar to the large-sample asymptotic expansions; however, the expansions here are in terms of the standard deviation of the disturbance terms. The results are then used to obtain the asymptotic bias and asymptotic mean squared prediction errors of the deterministic and stochastic predictors of a model containing the Box-Cox transformation.
Approximate Solutions to Stochastic Dynamic Programs
Authors: Stern Steven
Published: March 2009

This paper examines the properties of various approximation methods for solving stochastic dynamic programs in structural estimation problems. The problem addressed is evaluating the expected value of the maximum of available choices. The paper shows that approximating this by the maximum of expected values frequently has poor properties. It also shows that choosing a convenient distributional assumptions for the errors and then solving exactly conditional on the distributional assumption leads to small approximation errors even if the distribution is misspecified.
A Nonparametric Approach to the Estimation of Diffusion Processes, With an Application to a Short-Term Interest Rate Model
Authors: Jiang George J. , Knight John L.
Published: March 2009

In this paper, we propose a nonparametric identification and estimation procedure for an ltd diffusion process based on discrete sampling observations. The nonparametric kernel estimator for the diffusion function developed in this paper deals with general ltd diffusion processes and avoids any functional form specification for either the drift function or the diffusion function. It is shown that under certain regularity conditions the nonparametric diffusion function estimator is pointwise consistent and asymptotically follows a normal mixture distribution. Under stronger conditions, a consistent nonparametric estimator of the drift function is also derived based on the diffusion function estimator and the marginal density of the process. An application of the nonparametric technique to a short-term interest rate model involving Canadian daily 3-month treasury bill rates is also undertaken. The estimation results provide evidence for rejecting the common parametric or semiparametric specifications for both the drift and diffusion functions.
Curved Exponential Models in Econometrics
Authors: van Garderen Kees Jan
Published: March 2009

Curved exponential models have the property that the dimension of the minimal sufficient statistic is larger than the number of parameters in the model. Many econometric models share this feature. The first part of the paper shows that, in fact, econometric models with this property are necessarily curved exponential. A method for constructing an explicit set of minimal sufficient statistics, based on partial scores and likelihood ratios, is given. The difference in dimension between parameterand statistic and the curvature of these models have important consequences for inference. It is not the purpose of this paper to contribute significantly to the theory of curved exponential models, other than to show that the theory applies to many econometric models and to highlight some multivariate aspects. Using the methods developed in the first part, we show that demand systems, the single structural equation model, the seemingly unrelated regressions, and autoregressive models are all curved exponential models.
Optimal Prediction Under Asymmetric Loss
Authors: Christoffersen Peter F. , Diebold Francis X.
Published: March 2009

Prediction problems involving asymmetric loss functions arise routinely in many fields, yet the theory of optimal prediction under asymmetric loss is not well developed. We study the optimal prediction problem under general loss structures and characterize the optimal predictor. We compute the optimal predictor analytically in two leading tractable cases and show how to compute it numerically in less tractable cases. A key theme is that the conditionally optimal forecast is biased under asymmetric loss and that the conditionally optimal amount of bias is time varying in general and depends on higher order conditional moments. Thus, for example, volatility dynamics (e.g., GARCH effects) are relevant for optimal point prediction under asymmetric loss. More generally, even for models with linear conditionalmean structure, the optimal point predictor is in general nonlinear under asymmetric loss, which provides a link with the broader nonlinear time series literature.