968 resultados para elasticity modulus


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This paper investigates the relationship between trade openness and the size of government, both theoretically and empirically. We show that openness can increase the size of governments through two channels: (1) a terms of trade externality, whereby trade lowers the domestic cost of taxation and (2) the demand for insurance, whereby trade raises risk and public transfers. We provide a unified framework for studying and testing these two mechanisms. First, we show how their relative strength depends on a key parameter, the elasticity of substitution between domestic and foreign goods. Second, while the terms of trade externality leads to inefficiently large governments, the increase in public spending due to the demand for insurance is optimal. We show that large volumes of trade may result in welfare losses if the terms of trade externality is strong enough while small volumes of trade are always beneficial. Third, we provide new evidence on the positive association between openness and the size of government and test whether it is consistent with the terms of trade externality or the demand for insurance. Our findings suggest that the positive relationship is remarkably robust and that the terms of trade externality may be the driving force behind it, thus raising warnings that globalization may have led to inefficiently large governments.

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Existing models of equilibrium unemployment with endogenous labor market participation are complex, generate procyclical unemployment rates and cannot match unemployment variability relative to GDP. We embed endogenous participation in a simple, tractable job market matching model, show analytically how variations in the participation rate are driven by the cross-sectional density of home productivity near the participation threshold, andhow this density translates into an extensive-margin labor supply elasticity. A calibration of the model to macro data not only matches employment and participation variabilities but also generates strongly countercyclical unemployment rates. With some wage rigidity the model also matches unemployment variations well. Furthermore, the labor supply elasticity implied by our calibration is consistent with microeconometric evidence for the US.

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To evaluate the regulation of connexin expression by fluid pressure, we have studied the effects of elevated transmural urine pressure on Connexin43 (Cx43) and Cx26. We chose to focus on these two proteins out of the five connexins (Cx26, 43, 40, 37, and 45) which we found by RT-PCR to be expressed in the rat bladder, since in situ hybridization and immunofluorescence showed that Cx43 is the predominant connexin expressed by smooth muscle cells (SMC), whereas Cx26 is abundantly expressed only in the latter cell type. To evaluate whether these connexins are affected by changes in transmural urine pressure, we used a rat model of bladder outlet obstruction, in which a ligature is placed around the urethra. Under conditions of increased fluid pressure due to urine retention, we observed that the expression of both Cx43 and Cx26 increased at both transcript and protein levels, reaching a maximum 7-9 h after the ligature. Further analysis revealed that these changes were accounted for by a fourfold increase in Cx43 mRNA of SMC but not urothelial cell and by a fivefold increase in Cx26 mRNA of urothelium. Scrape-loading of propidium iodide showed that the latter change was paralleled by a twofold increase in coupling between urothelial cells. The data show that Cx43 and Cx26 are differentially regulated during bladder outlet obstruction and contribute to the response of the bladder wall to increased voiding pressure, possibly to control its elasticity.

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As the prevalence of smoking has decreased to below 20%, health practitioners interest has shifted towards theprevalence of obesity, and reducing it is one of the major health challenges in decades to come. In this paper westudy the impact that the final product of the anti-smoking campaign, that is, smokers quitting the habit, had onaverage weight in the population. To these ends, we use data from the Behavioral Risk Factors Surveillance System,a large series of independent representative cross-sectional surveys. We construct a synthetic panel that allows us tocontrol for unobserved heterogeneity and we exploit the exogenous changes in taxes and regulations to instrumentthe endogenous decision to give up the habit of smoking. Our estimates, are very close to estimates issued in the 90sby the US Department of Health, and indicate that a 10% decrease in the incidence of smoking leads to an averageweight increase of 2.2 to 3 pounds, depending on choice of specification. In addition, we find evidence that the effectovershoots in the short run, although a significant part remains even after two years. However, when we split thesample between men and women, we only find a significant effect for men. Finally, the implicit elasticity of quittingsmoking to the probability of becoming obese is calculated at 0.58. This implies that the net benefit from reducingthe incidence of smoking by 1% is positive even though the cost to society is $0.6 billions.

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This paper analyses the effect of tobacco prices on the propensity tostart and quit smoking using a pool of the 1993, 1995 and 1997 editionsof the Spanish National Health Surveys. The estimates for severalparametric models of the hazard rate for starting and quitting suggestthat i) The public health measures applied as of 1992 have had asignificative effect on both reducing the hazard of starting andincreasing the hazard of quitting, ii) Prices have a very weak effect onthe hazard of starting in the male population and no significant effectin the female population, iii) The price floor of cigarrettes, proxiedby the average price of a pack of black cigarrettes, has a significanteffect on the quitting hazard which is robust across specifications andapplies to both men and women. The implied price elasticity of the timeup to quitting is situated around -1.4.

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We analyze a monetary model with flexible labor supply, cash-inadvance constraints and seigniorage-financed government deficits. If the intertemporal elasticity of substitution of labor is greater than one, there are two steady states, one determinate and the other indeterminate. If the elasticity is less than one, there is a unique steady state, which can be indeterminate. Only in the latter case do there exist sunspot equilibria that are stable under adaptive learning. A sufficient reduction in government purchases can in many cases eliminate the sunspot equilibria while raising consumption/labor taxes even enough to balance the budget may fail to achieve determinacy.

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This paper reports an analysis of the evolution of equity in access to health care in Spain over the period 1987-2001, a time span covering the development of the modern Spanish National Health System. Our measures of access are the probabilities of visiting a doctor, using emergency services and being hospitalised. For these three measures we obtain indices of horizontal inequity from microeconometric models of utilization that exploit the individual information in the Spanish National Health Surveys of 1987 and 2001. We find that by 2001 the system has improved in the sense that differences in income no longer lead to different access given the same level of need. However, the tenure of private health insurance leads to differences in access given the same level of need, and its contribution to inequity has increased over time, both because insurance is more concentrated among the rich and because the elasticity of utilization for the three services has increased too.

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Despite the importance of supplier inducement and brand loyalty inthe drug purchasing process, little empirical evidence is to be foundwith regard to the influence that these factors exert on patients decisions. Under the new scenario of easier access to information,patients are becoming more demanding and even go as far asquestioning their physicians prescription. Furthermore, newregulation also encourages patients to adopt an active role in thedecision between brand-name and generic drugs. Using a statedpreference model based on a choice survey, I have found evidenceof how significant physicians prescription and pharmacists recommendation become throughout the drug purchase process and,to what extent, brand loyalty influences the final decision. Asfar as we are aware, this paper is the first to explicitlytake consumers preferences into account rather than focusingon the behavior of health professionals.

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In this paper we present a simple theory-based measure of the variations in aggregate economic efficiency: the gap between the marginal product of labor and the household s consumption/leisure tradeoff. We show that this indicator corresponds to the inverse of the markup of price over social marginal cost, and give some evidence in support of this interpretation. We then show that, with some auxilliary assumptions our gap variable may be used to measure the efficiency costs of business fluctuations. We find that the latter costs are modest on average. However, to the extent the flexible price equilibrium is distorted,the gross efficiency losses from recessions and gains from booms may be large. Indeed, we find that the major recessions involved large efficiency losses. These results hold for reasonable parameterizations of the Frisch elasticity of labor supply, the coefficient of relative risk aversion, and steady state distortions.

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An attendance equation is estimated using data on individual games playedin the Spanish First Division Football League. The specification includesas explanatory factors: economic variables, quality, uncertainty andopportunity costs. We concentrate the analysis on some specificationissues such as controlling the effect of unobservables given the paneldata structure of the data set, the type of functional form and thepotential endogeneity of prices. We obtain the expected effects onattendance for all the variables. The estimated price elasticities aresmaller than one in absolute value as usually occurs in this literaturebut are sensitive to the specification issues.

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This paper exploits an unusual transportation setting to estimate the value of a statistical life(VSL). We estimate the trade-offs individuals are willing to make between mortality risk andcost as they travel to and from the international airport in Sierra Leone (which is separated fromthe capital Freetown by a body of water). Travelers choose from among multiple transportoptions ? namely, ferry, helicopter, hovercraft, and water taxi. The setting and original datasetallow us to address some typical omitted variable concerns in order to generate some of the firstrevealed preference VSL estimates from Africa. The data also allows us to compare VSLestimates for travelers from 56 countries, including 20 African and 36 non-African countries, allfacing the same choice situation. The average VSL estimate for African travelers in the sample isUS$577,000 compared to US$924,000 for non-Africans. Individual characteristics, particularlyjob earnings, can largely account for the difference between Africans and non-Africans; Africansin the sample typically earn somewhat less. There is little evidence that individual VSL estimatesare driven by a lack of information, predicted life expectancy, or cultural norms around risktakingor fatalism. The data implies an income elasticity of the VSL of 1.77. These revealedpreference VSL estimates from a developing country fill an important gap in the existingliterature, and can be used for a variety of public policy purposes, including in current debateswithin Sierra Leone regarding the desirability of constructing new transportation infrastructure.

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The calculation of elasticity parameters by sonic and ultra sonic wave propagation in saturated soils using Biot's theory needs the following variables : forpiation density and porosity (p, ø), compressional and shear wave velocities (Vp, Vs), fluid density, viscosity and compressibility (Pfi Ilfi Ki), matrix density and compressibility (p" K), The first four parameters can be determined in situ using logging probes. Because fluid and matrix characteristics are not modified during core extraction, they can be obtained through laboratory measurements. All parameters necessitate precise calibrations in various environments and for specific range of values encountered in soils. The slim diameter of boreholes in shallow geophysics and the high cost of petroleum equipment demand the use of specific probes, which usually only give qualitative results. The measurement 'of density is done with a gamma-gamma probe and the measurement of hydrogen index, in relation to porosity, by a neutron probe. The first step of this work has been carried out in synthetic formations in the laboratory using homogeneous media of known density and porosity. To establish borehole corrections different casings have been used. Finally a comparison between laboratory and in situ data in cored holes of known geometry and casing has been performed.

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Fully biodegradable composite materials were obtained through reinforcement of a commercially available thermoplastic starch (TPS) matrix with rapeseed fibers (RSF). The influence of reinforcement content on the water sorption capacity, as well as thermal and thermo-mechanical properties of composites were evaluated. Even though the hydrophilic character of natural fibers tends to favor the absorption of water, results demonstrated that the incorporation of RSF did not have a significant effect on the water uptake of the composites. DSC experiments showed that fibers restricted the mobility of the starch macromolecules from the TPS matrix, hence reducing their capacity to crystallize. The viscoelastic behaviour of TPS was also affected, and reinforced materials presented lower viscous deformation and recovery capacity. In addition, the elasticity of materials was considerably diminished when increasing fiber content, as evidenced in the TMA and DMTA measurements

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The net mechanical efficiency of positive work (eta(pos)) has been shown to increase if it is immediately preceded by negative work. This phenomenon is explained by the storage of elastic energy during the negative phase and its release during the subsequent positive phase. If a transition time (T) takes place, the elastic energy is dissipated into heat. The aim of the present study was to investigate the relationship between eta(pos) and T, and to determine the minimal T required so that eta(pos) reached its minimal value. Seven healthy male subjects were tested during four series of lowering-raising of the body mass. In the first series (S (0)), the negative and positive phases were executed without any transition time. In the three other series, T was varied by a timer (0.12, 0.24 and 0.56 s for series S (1), S (2) and S (3), respectively). These exercises were performed on a force platform sensitive to vertical forces to measure the mechanical work and a gas analyser was used to determine the energy expenditure. The results indicated that eta(pos) was the highest (31.1%) for the series without any transition time (S (0)). The efficiencies observed with transition times (S (1), S (2) and S (3)) were 27.7, 26.0 and 23.8%, respectively, demonstrating that T plays an important role for mechanical efficiency. The investigation of the relationship between eta(pos) and T revealed that the minimal T required so that eta(pos) reached its minimal value is 0.59 s.

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Pulse-wave velocity (PWV) is considered as the gold-standard method to assess arterial stiffness, an independent predictor of cardiovascular morbidity and mortality. Current available devices that measure PWV need to be operated by skilled medical staff, thus, reducing the potential use of PWV in the ambulatory setting. In this paper, we present a new technique allowing continuous, unsupervised measurements of pulse transit times (PTT) in central arteries by means of a chest sensor. This technique relies on measuring the propagation time of pressure pulses from their genesis in the left ventricle to their later arrival at the cutaneous vasculature on the sternum. Combined thoracic impedance cardiography and phonocardiography are used to detect the opening of the aortic valve, from which a pre-ejection period (PEP) value is estimated. Multichannel reflective photoplethysmography at the sternum is used to detect the distal pulse-arrival time (PAT). A PTT value is then calculated as PTT = PAT - PEP. After optimizing the parameters of the chest PTT calculation algorithm on a nine-subject cohort, a prospective validation study involving 31 normo- and hypertensive subjects was performed. 1/chest PTT correlated very well with the COMPLIOR carotid to femoral PWV (r = 0.88, p < 10 (-9)). Finally, an empirical method to map chest PTT values onto chest PWV values is explored.