Candidate Instruments Research Articles

Indirect Taxes on International Aviation*

AbstractThere has recently been much discussion of the possible use of internationally coordinated indirect taxes, or equivalent charges, on international aviation, whether as a source of finance for development or as part of a response to heightened concerns with climate change. This paper considers the strengths and weaknesses of the leading candidate instruments of this kind. It argues that, on both policy and administration grounds, the case for increasing indirect taxes on international aviation is strong: the indirect tax burden on international aviation is very low, yet aviation contributes significantly to border‐crossing environmental damage, is just as proper an object of taxation as any other commodity, and incipient tax competition is likely to result in these taxes being set at inefficiently low levels. But the form(s) in which such taxes are levied matters: a tax on aviation fuel would address the key border‐crossing externalities most directly; a tax on final ticket values would have greater revenue potential, and perhaps some distributional advantage; departure/arrival taxes face the least legal obstacles, but are much blunter instruments. Optimal policy, it is shown, typically requires deploying both a fuel tax and a ticket tax, and the paper explores, both in principle and by simulation, the key considerations and trade‐offs involved in designing a suitable indirect tax regime for international aviation.

Developing a baseline assessment battery: balancing patient time burden with essential clinical and research monitoring.

Baseline assessment in a multisite alcohol-dependence treatment study has several purposes: addressing inclusion/exclusion criteria and characterizing participants to illuminate subsequent efficacy and safety patterns of the interventions. Combination pharmacotherapy and behavioral therapy trials, however, require more complex assessments than single-modality studies. Medication trials require measures of initial safety for study drug as well as for subsequent side-effect and adverse-effect monitoring (e.g., physical examination, laboratory markers, somatic symptoms, medical conditions and concomitant medications). Behavioral therapy trials (and in some cases medication trials) warrant baseline measurement of mediators of therapy effect (e.g., prior treatment history, motivation for change, self-efficacy, other psychiatric conditions, treatment expectations and network supports). Measures may be needed to interpret interactions that may be discovered between these modalities. The National Institute on Alcohol Abuse and Alcoholism COMBINE Study evaluated the potentially overwhelming number of candidate instruments through an iterative process, using the following sequence to finalize a rational baseline assessment battery: key constructs, representative measures, determination of duration of assessment, risk of assessment reactivity, goal priorities, necessity for measure "pruning" and order of measure presentation. After selecting the draft battery, feasibility was evaluated in a pilot study prior to the main trial. The battery was feasible to administer and avoided unintended selection bias. Dropout was substantial, however, and differences across sites in baseline assessment completion rates reflected a tendency of a central intake model to function as an initial filter of dropouts, compared with a direct recruitment model. This process holds several potentially useful lessons for investigators.

An Evaluation of Instrumental Variable Strategies for Estimating the Effects of Catholic Schooling

Several previous studies have relied on religious affiliation and the proximity to Catholic schools as exogenous sources of variation for identifying the effect of Catholic schooling on a wide variety of outcomes. Using three separate approaches, we examine the validity of these instrumental variables. We find that none of the candidate instruments is a useful source of identification in currently available data sets. We also investigate the role of exclusion restrictions versus nonlinearity as the source of identification in bivariate probit models. The analysis may be useful as a template for the assessment of instrumental variables strategies in other applications.

A sensitivity study on spectroscopic parameter accuracies for a mm/sub-mm limb sounder instrument

The purpose of this paper is to perform a detailed error analysis for a mm/sub-mm limb sounding instrument with respect to spectroscopic parameters. This is done in order to give some insight into the most crucial spectroscopic parameters and to work out a list of recommendations for measurements that would yield the largest possible benefit for an accurate retrieval. The investigations cover a variety of spectroscopic line parameters, such as line intensity, line position, air and self broadening parameters and their temperature exponents, and pressure shift. The retrieval process is performed with the optimal estimation method (OEM). The OEM allows one to perform an assessment of the total statistical error, as well as of the model parameter error, such as the error coming from spectroscopic parameters. The instrument parameters assumed are those of the MASTER instrument studied by the European Space Agency, one of the candidate instruments for a future atmospheric chemistry mission. However, the same principle and method of analysis can be applied to any other millimeter/sub-millimeter limb sounding instrument, for instance the Japanese instrument JEM/SMILES, the Swedish instrument Odin, and the Earth Observing System Microwave Limb Sounder. We find that an uncertainty in the intensity of the strong lines give an error of similar magnitude on the retrieved species to which the lines belong. Uncertainties in the line position have overall a small impact on the retrieval, indicating that the line positions are known with sufficient accuracy. The air broadening parameters and their temperature exponents of a few strong lines dominate the error budget. On the other hand, the self broadening parameters and the pressure shifts are found to have a rather small impact on the retrieval.

Assessment of patients with psoriatic arthritis: a review of currently available measures.

To date, specific measures to assess disease activity in PsA have not been validated. The tools used for assessment of psoriatic peripheral joint disease have been borrowed from the assessment of RA. While, in general, some of these outcome measures perform well in PsA, the distinct distribution of joint involvement coupled with the unique patterns of synovitis and periarticular inflammation demand that these measures be appropriately and carefully adapted. In order to capture the wide variation that characterizes the clinical presentation seen among patients with PsA, a larger number of joints should be assessed. Moreover, because of the frequency and severity of back involvement in PsA, assessment of spinal mobility and pain is required. Many clinical methods used to assess axial disease in AS have not proven to be reliable, and even measures deemed appropriate in AS require validation in PsA. Specific assessment of common features of PsA, including dactylitis, enthesitis, and tendonitis, requires further study. In addition, available techniques for radiographic evaluation of patients with RA may not fully record the specific changes noted among patients with PsA. Moreover, the utility of newer imaging techniques in the assessment of joint and spinal inflammation in patients with PsA requires further study. Finally, it is important to evaluate whether the same instruments can be used for the various patterns of PsA. Rigorous validation of currently used techniques, combined with the development of new assessment tools, is urgently required to fully assess the therapeutic response in PsA. In our view, a consensus development of a core set of outcome domains, psychometric evaluation of candidate instruments in patients with PsA, and construction of response criteria from clinical trials that have used such instruments constitute the research agenda for PsA.

Atmospheres panel report to the payload panel

This report is the outgrowth of the Atmospheres Panel meeting held in September 1991. The Panel was asked to either endorse or reject the CEES and IPCC research priorities for global change and to indicate which EOS candidate instruments, in the Panel's opinion, made the most significant contributions to answering the scientific questions associated with the CEES and IPCC priorities. After some discussion, the Panel endorsed the CEES and IPPC priorities as presented by Dr. Watson at the Seattle IWG. However, the Panel remained very concerned about significant weakness in the proposed stratospheric instrument package associated with hydroxyl and halogen measurements. This concern is expressed in our recommendation list below. This report is divided into five sections. The first section is a summary of recommendations of the Panel. The summary contains the list of primary instruments needed to answer the major science questions which the Panel has identified. The four sections following detail our recommendations. They are: (1) Clouds, Radiation and Precipitation, (2) Tropospheric Chemistry, (3) Stratospheric Chemistry and Dynamics and (4) Data Assimilation. While the separation of these issues may seem artificial, these four categories represent the cores of merging disciplines within the atmospheric sciences. In order to expose the reasoning behind instrument prioritization, the Panel reiterated the key science questions and then discussed the approach used to answer those questions. From the approach, measurement needs and instrument priorities follow logically. Additional subsections briefly discuss constraints on the remote measurements (if any) and other relevant measurement programs (if any); major recommendations follow. EOS instruments matching the data requirements for a given science objective are divided into three categories: Primary, Ancillary and Contributing. The order of listing within the category does not indicate prioritization; it is random. A Primary Instrument is one directly relevant to the core science questions. A Contributing Instrument is one whose measurement would add to the overall pool of information in a positive way, but loss of data from that instrument would not cripple the science objectives as would loss of data from a Primary Instrument. Ancillary Instruments occupy the gray area in between. The Panel recognizes the measurements made by Ancillary Instruments as contributing significantly to some science objectives, but not all Panel members felt that an ancillary instrument was core to a given science objective.

Science aspects of a mission beyond the planets

A mission out of the planetary system, launched about the year 2000, could provide valuable data concerning characteristics of the heliopause, the interstellar medium, stellar distances (by parallax measurements), low-energy cosmic rays, interplanetary gas distribution, and mass of the solar system. Secondary objectives include investigation of Pluto. Candidate science measurements, instruments, and instrument development needs are discussed. The mission should extend from 400 to 1000 AU from the Sun. A heliocentric hyperbolic escape velocity of 50–100 km/sec or more is needed to attain this distance within a reasonable mission duration (20–50 years). The trajectory should be toward the incoming interstellar gas. For a year 2000 launch, a Pluto encounter and orbiter can be included. A second mission targeted parallel to the solar axis would also be worthwhile.

Instrumentation trends in nuclear medicine

Nuclear medicine instrumentation requires use of various configurations of photon detectors for the purpose of in vivo and in vitro measurements of flow and metabolism. Computed tomography has solved a previous limitation of an ambiguous volume of interest intrinsic to projection images. Selection of instruments involves first, a definition of the medical problem to be solved; then an evaluation of the following characteristics of the candidate instruments: sensitivity, spatial resolution, saturation performance, dead time, uniformity of resolution, uniformity of sensitivity, data processing capabilities, and cost. New developments include dynamic imaging in transverse section with either single photon or positron annihilation photons, and whole-body quantitative imaging of sequential changes in radiopharmaceutical concentration.