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on Computational Economics |
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Issue of 2004‒12‒20
twelve papers chosen by |
| By: | Jahn, Olaf; Möhring, Rolf; Schulz, Andreas; Stier Moses, Nicolás |
| Abstract: | The design of route-guidance systems faces a well-known dilemma. The approach that theoretically yields the system-optimal traffic pattern may discriminate against some users, for the sake of favoring others. Proposed alternate models, however, do not directly address the system perspective and may result in inferior performance. We propose a novel model and corresponding algorithms to resolve this dilemma. We present computational results on real-world instances and compare the new approach with the well-established traffic assignment model. The quintessence is that system-optimal routing of traffic flow with explicit integration of user constraints leads to a better performance than the user equilibrium while simultaneously guaranteeing a superior fairness compared to the pure system optimum. |
| Keywords: | Intelligent Transportation Systems, Route Guidance, Traffic Flow, System Optimum, User Equilibrium, Multicommodity Flow, Constrained Shortest Path, |
| Date: | 2004–12–10 |
| URL: | http://d.repec.org/n?u=RePEc:mit:sloanp:7380&r=cmp |
| By: | Mototsugu Shintani (Department of Economics, Vanderbilt University); Oliver Linton (Department of Economics, London School of Economics) |
| Abstract: | This paper derives the asymptotic distribution of the nonparametric neural network estimator of the Lyapunov exponent in a noisy system. Positivity of the Lyapunov exponent is an operational definition of chaos. We introduce a statistical framework for testing the chaotic hypothesis based on the estimated Lyapunov exponents and a consistent variance estimator. A simulation study to evaluate small sample performance is reported. We also apply our procedures to daily stock return data. In most cases, the hypothesis of chaos in the stock return series is rejected at the 1% level with an exception in some higher power transformed absolute returns. |
| Keywords: | Artificial neural networks, nonlinear dynamics, nonlinear time series, nonparametric regression, sieve estimation |
| JEL: | C14 C22 |
| Date: | 2003–05 |
| URL: | http://d.repec.org/n?u=RePEc:van:wpaper:0309&r=cmp |
| By: | Barbara Berkel and Axel Börsch-Supan (Mannheim Research Institute for the Economics of Aging (MEA)) |
| Abstract: | The financing problems beleaguering the public pension system have again shifted the spotlight onto the retirement age. This paper examines the impact of various reform options on the actual retirement choices of older workers. The paper focuses in particular on the long-term implications of the changes implemented in pension legislation since 1992 and the reform options discussed by the German Social Security Reform Commission installed in 2002, the so called "Rürup Commission". Our simulations show that the early-retirement pension adjustment factors introduced by the 1992 pension reform will, in the long term, raise the average effective age of retirement for men by somewhat less than two years. The across-the-board two-year increase in all the relevant age limits proposed by the "Rürup Commission" would raise the effective average age of retirement of men by about eight months. If the actuarial adjustment factor is increased from 3.6% to 6% per year, the effective average retirement age rises by almost two years. The effects are considerably weaker for women. |
| Date: | 2003–09–15 |
| URL: | http://d.repec.org/n?u=RePEc:xrs:meawpa:0336&r=cmp |
| By: | Petra Ahrweiler (Research Center Media and Politics, Institute for Political Science, University of Hamburg, Germany); Andreas Pyka (University of Augsburg, Department of Economics); Nigel Gilbert (School of Human Sciences, University of Surrey, Guildford, Surrey, GU2 7XH, United Kingdom) |
| Abstract: | An agent-based simulation model representing a theory of the dynamic processes involved in innovation in modern knowledge-based industries is described. The agent-based approach allows the representation of heterogeneous agents that have individual and varying stocks of knowledge. The simulation is able to model uncertainty, historical change, effect of failure on the agent population, and agent learning from experience, from individual research and from partners and collaborators. The interactions between the agents occur on two levels: through a market with firms supplying and consuming goods for a price, and through the exchange of knowledge. A brief description of the implementation of the model and its user interface is given. |
| Keywords: | innovation networks, agent-based modelling |
| JEL: | O31 O32 L22 |
| Date: | 2004–12 |
| URL: | http://d.repec.org/n?u=RePEc:aug:augsbe:0267&r=cmp |
| By: | John Creedy (Department of Economics, The University of Melbourne); Guyonne Kalb (Melbourne Institute of Applied Economic and Social Research, The University of Melbourne); Hsein Kew (Department of Economics, The University of Melbourne) |
| Abstract: | This paper addresses the need for a measure of the uncertainty that is associated with the results calculated through tax policy behavioural microsimulation modelling. Deriving the analytical measure would be extremely complicated. Therefore, a simulated approach is proposed which generates a pseudo sampling distribution of aggregate measures based on the sampling distribution of the estimated labour supply parameters. This approach, which is very computer intensive, is compared to a more time-efficient approach where the functional form of the sampling distribution is assumed to be normal. The results show that in many instances the results from the two approaches are quite similar. The exception is when aggregate measures for minor types of payments, involving relatively small groups of the population, are examined. |
| Date: | 2004–12 |
| URL: | http://d.repec.org/n?u=RePEc:iae:iaewps:wp2004n32&r=cmp |
| By: | Axel Börsch-Supan, Alexander Ludwig, Joachim Winter (Mannheim Research Institute for the Economics of Aging (MEA)) |
| Abstract: | We present a quantitative analysis of international capital flows induced by differ-ential population aging and pension reform. It is well known that within each country, demo-graphic change alters the time path of aggregate savings. This process may be amplified if pension reform shifts old-age provision towards more pre-funding. While the patterns of population aging are similar in most countries, timing and initial conditions differ substan-tially. Hence, to the extent that capital is internationally mobile, population aging will induce capital flows between countries. In order to quantify these effects, we develop a multi-country overlapping generations model and use long-term demographic projections for several world regions to project international capital flows in the course of population aging. Our simula-tions suggest that capital flows from fast-aging industrial countries such as Germany, Italy or Japan to the rest of the world will be substantial. We also conclude that closed-economy mod-els of pension reform miss quantitatively important effects of international capital mobility. |
| Date: | 2003–04–09 |
| URL: | http://d.repec.org/n?u=RePEc:xrs:meawpa:0328&r=cmp |
| By: | Ahuja, Ravindra; Kumar, Arvind; Jha, Krishna; Orlin, James |
| Abstract: | The Weapon Target Assignment (WTA) problem is a fundamental problem arising in defense-related applications of operations research. This problem consists of optimally assigning n weapons to m targets so that the total expected survival value of the targets after all the engagements is minimum. The WTA problem can be formulated as a nonlinear integer programming problem and is known to be NP-complete. There do not exist any exact methods for the WTA problem which can solve even small size problems (for example, with 20 weapons and 20 targets). Though several heuristic methods have been proposed to solve the WTA problem, due to the absence of exact methods, no estimates are available on the quality of solutions produced by such heuristics. In this paper, we suggest linear programming, integer programming, and network flow based lower bounding methods using which we obtain several branch and bound algorithms for the WTA problem. We also propose a network flow based construction heuristic and a very large-scale neighborhood (VLSN) search algorithm. We present computational results of our algorithms which indicate that we can solve moderately large size instances (up to 80 weapons and 80 targets) of the WTA problem optimally and obtain almost optimal solutions of fairly large instances (up to 200 weapons and 200 targets) within a few seconds. |
| Keywords: | Weapon Target Assignment, WTA, very large-scale neighborhood search algorithm, |
| Date: | 2004–12–10 |
| URL: | http://d.repec.org/n?u=RePEc:mit:sloanp:7388&r=cmp |
| By: | Alwyn Young |
| Abstract: | This paper simulates the impact of the AIDS epidemic on future living standards in South Africa. I emphasize two competing effects. On the one hand, the epidemic is likely to have a detrimental impact on the human capital accumulation of orphaned children. On the other hand, widespread community infection lowers fertility, both directly, through a reduction in the willingness to engage in unprotected sexual activity, and indirectly, by increasing the scarcity of labour and the value of a woman's time. I find that even with the most pessimistic assumptions concerning reductions in educational attainment, the fertility effect dominates. The AIDS epidemic, on net, enhances the future per capita consumption possibilities of the South African economy. |
| JEL: | O1 |
| Date: | 2004–12 |
| URL: | http://d.repec.org/n?u=RePEc:nbr:nberwo:10991&r=cmp |
| By: | Jonathan Gruber |
| Abstract: | Despite a $140 billion existing tax break for employer-provided health insurance, tax policy remains the tool of choice for many policy-makers in addressing the problem of the uninsured. In this paper, I use a microsimulation model to estimate the impact of various tax interventions to cover the uninsured, relative to an expansion of public insurance designed to accomplish the same goals. I contrast the efficiency of these policies along several dimensions, most notably the dollars of public spending per dollar of insurance value provided. I find that every tax policy is much less efficient than public insurance expansions: while public insurance costs the government only between $1.17 and $1.33 per dollar of insurance value provided, tax policies cost the government between $2.36 and $12.98 per dollar of insurance value provided. I also find that targeting is crucial for efficient tax policy; policies tightly targeted to the lowest income earners have a much higher efficiency than those available higher in the income distribution. Within tax policies, tax credits aimed at employers are the most efficient, and tax credits aimed at employees are the least efficient, because the single greatest determinant of insurance coverage is being offered insurance by your employer, and because most employees who are offered already take up that insurance. Tax credits targeted at non-group coverage are fairly similar to employer tax credits at low levels, but much less efficient at higher levels. |
| JEL: | H2 I1 |
| Date: | 2004–12 |
| URL: | http://d.repec.org/n?u=RePEc:nbr:nberwo:10977&r=cmp |
| By: | Zhou Yang; Donna B. Gilleskie; Edward C. Norton |
| Abstract: | There is much debate about whether the Medicare Prescription Drug Bill %u2013 the greatest expansion of Medicare benefits since its creation in 1965 %u2013 will improve the health of elderly Americans, and how much it will cost. We model how insurance affects medical care utilization, and subsequently, health outcomes over time in a dynamic model with correlated errors. Longitudinal individual-level data from the 1992-1998 Medicare Current Beneficiary Survey provide estimates of these effects. Simulations over five years show that expanding prescription drug coverage would increase drug expenditures by between 12% and 17%. However, other health care expenditures would only increase slightly, and the mortality rate would improve. |
| JEL: | I12 I18 H5 |
| Date: | 2004–12 |
| URL: | http://d.repec.org/n?u=RePEc:nbr:nberwo:10964&r=cmp |
| By: | Palacios, Rafael; Gupta, Amar; Wang, Patrick |
| Abstract: | In recent years, a number of large-scale applications continue to rely heavily on the use of paper as the dominant medium, either on intra-organization basis or on inter-organization basis, including paper intensive applications in the check processing application. In many countries, the value of each check is read by human eyes before the check is physically transported, in stages, from the point it was presented to the location of the branch of the bank which issued the blank check to the concerned account holder. Such process of manual reading of each check involves significant time and cost. In this research, a new approach is introduced to read the numerical amount field on the check; also known as the courtesy amount field. In the case of check processing, the segmentation of unconstrained strings into individual digits is a challenging task because one needs to accommodate special cases involving: connected or overlapping digits, broken digits, and digits physically connected to a piece of stroke that belongs to a neighboring digit. The system described in this paper involves three stages: segmentation, normalization, and the recognition of each character using a neural network classifier, with results better than many other methods in the literaratur |
| Keywords: | Character recognition, bank check recognition, segmentation, courtesy amount, scanning, preprocessing, accuracy rate, post processing, feedback, architecture, |
| Date: | 2004–12–10 |
| URL: | http://d.repec.org/n?u=RePEc:mit:sloanp:7379&r=cmp |
| By: | Deni Khanafiah (Bandung Fe Institute); Hokky Situngkir (Bandung Fe Institute) |
| Abstract: | Cellular phone is one of the most developing technological artifacts today. The evolution occurs through random innovation. Our effort is trying to view the evolution of this artifact from memetics. By constructing a phylomemetic tree based on cellular phone memes to infer or estimate the evolutionary history and relationship among cellular phone. We adopt several methods, which are commonly used in constructing phylogenetic tree, they are UPGMA algorithm and Parsimony Maximum algorithm to construct cellphone phylomemetic tree. Therefore we compare with the innovation tree, which is based on serial number and their appearance time. From phylomemetic tree, we then analyze the process of a cellular phone innovation through looking out on the cellular phone type lies in the same cluster. The comparison of the simulation tree result shows a generally different branching pattern, giving a presumption that innovation in cellular phone is not really relating with their serial number, but occurs merely because of random mutation of allomeme design and competes with its technological development. |
| Keywords: | artifact, innovation, evolution, memetics, phylomemetic tree, cellular phone. |
| JEL: | L |
| Date: | 2004–12–17 |
| URL: | http://d.repec.org/n?u=RePEc:wpa:wuwpio:0412009&r=cmp |