Costly search and design

Firms compete by choosing both a price and a design from a family of designs thatcan be represented as demand rotations. Consumers engage in costly sequential searchamong firms. Each time a consumer pays a search cost he observes a new offering. Anoffering consists of a price quote and a new good, where goods might vary in the extentto which they are good matches for the consumer. In equilibrium, only two design-styles arise: either the most niche where consumers are likely to either love or loathethe product, or the broadest where consumers are likely to have similar valuations. Inequilibrium, different firms may simultaneously offer both design-styles. We performcomparative statics on the equilibrium and show that a fall in search costs can lead tohigher industry prices and profits and lower consumer surplus. Our analysis is relatedto discussions of how the internet has led to the prevalence of niche goods and the"long tail" phenomenon.

Implementation, elimination of weakly dominated strategies and evolutionary dynamics

This paper is concerned with the realism of mechanisms that implementsocial choice functions in the traditional sense. Will agents actually playthe equilibrium assumed by the analysis? As an example, we study theconvergence and stability properties of Sj\"ostr\"om's (1994) mechanism, onthe assumption that boundedly rational players find their way to equilibriumusing monotonic learning dynamics and also with fictitious play. Thismechanism implements most social choice functions in economic environmentsusing as a solution concept the iterated elimination of weakly dominatedstrategies (only one round of deletion of weakly dominated strategies isneeded). There are, however, many sets of Nash equilibria whose payoffs maybe very different from those desired by the social choice function. Withmonotonic dynamics we show that many equilibria in all the sets ofequilibria we describe are the limit points of trajectories that havecompletely mixed initial conditions. The initial conditions that lead tothese equilibria need not be very close to the limiting point. Furthermore,even if the dynamics converge to the ``right'' set of equilibria, it stillcan converge to quite a poor outcome in welfare terms. With fictitious play,if the agents have completely mixed prior beliefs, beliefs and play convergeto the outcome the planner wants to implement.

Optimal information transmission in organizations: Search and congestion

We propose a stylized model of a problem-solving organization whoseinternal communication structure is given by a fixed network. Problemsarrive randomly anywhere in this network and must find their way to theirrespective specialized solvers by relying on local information alone.The organization handles multiple problems simultaneously. For this reason,the process may be subject to congestion. We provide a characterization ofthe threshold of collapse of the network and of the stock of foatingproblems (or average delay) that prevails below that threshold. We buildupon this characterization to address a design problem: the determinationof what kind of network architecture optimizes performance for any givenproblem arrival rate. We conclude that, for low arrival rates, the optimalnetwork is very polarized (i.e. star-like or centralized ), whereas it islargely homogenous (or decentralized ) for high arrival rates. We also showthat, if an auxiliary assumption holds, the transition between these twoopposite structures is sharp and they are the only ones to ever qualify asoptimal.

A search theory of money and commerce with Neoclassical production

This paper advances a highly tractable model with search theoretic foundations for money and neoclassical growth. In the model, manufacturingand commerce are distinct and separate activities. In manufacturing,goods are efficiently produced combining capital and labor. In commerce,goods are exchanged in bilateral meetings. The model is applied to studythe effects of inßation on capital accumulation and welfare. With realisticparameters, inflation has large negative effects on welfare even though itraises capital and output. In contrast, with cash-in-advance, a deviceinformally motivated with bilateral trading, inflation depresses capitaland output and has a negligible effect on welfare.

A simple optimised search heuristic for the job-shop scheduling problem

This paper presents a simple Optimised Search Heuristic for the Job Shop Scheduling problem that combines a GRASP heuristic with a branch-and-bound algorithm. The proposed method is compared with similar approaches and leads to better results in terms of solution quality and computing times.

How to recognize opportunities: Heterarchical search in a Wall Street trading room

Our task in this paper is to analyze the organization of trading in the era of quantitativefinance. To do so, we conduct an ethnography of arbitrage, the trading strategy that bestexemplifies finance in the wake of the quantitative revolution. In contrast to value andmomentum investing, we argue, arbitrage involves an art of association - the constructionof equivalence (comparability) of properties across different assets. In place of essentialor relationa l characteristics, the peculiar valuation that takes place in arbitrage is based on an operation that makes something the measure of something else - associating securities to each other. The process of recognizing opportunities and the practices of making novel associations are shaped by the specific socio-spatial and socio-technical configurations of the trading room. Calculation is distributed across persons and instruments as the trading room organizes interaction among diverse principles of valuation.

Complementarity between technology make and buy in innovation strategies: Evidence from Belgiam manufacturing firms

This paper characterizes the innovation strategy of manufacturing firms andexamines the relation between the innovation strategy and importantindustry-, firm- and innovation-specific characteristics using Belgiandata from the Eurostat Community Innovation Survey. In addition to importantsize effects explaining innovation, we find that high perceived risks andcosts and low appropriability of innovations do not discourage innovation,but rather determine how the innovation sourcing strategy is chosen. Withrespect to the determinants of the decision of the innovative firm toproduce technology itself (Make) or to source technology externally (Buy),we find that small firms are more likely restrict their innovation strategyto an exclusive make or buy strategy, while large firms are more likely tocombine both internal and external knowledge acquisition in their innovationstrategy. An interesting result that highlights the complementary nature ofthe Make and Buy decisions, is that, controlled for firm size, companies forwhich internal information is an important source for innovation are morelikely to combine internal and external sources of technology. We find thisto be evidence of the fact that in-house R&D generates the necessaryabsorptive capacity to profit from external knowledge acquisition. Also theeffectiveness of different mechanisms to appropriate the benefits ofinnovations and the internal organizational resistance against change areimportant determinants of the firm's technology sourcing strategy.

Non-stationary job search when jobs are not forever: A structural estimation

This paper considers a job search model where the environment is notstationary along the unemployment spell and where jobs do not lastforever. Under this circumstance, reservation wages can be lower thanwithout separations, as in a stationary environment, but they can alsobe initially higher because of the non-stationarity of the model. Moreover,the time-dependence of reservation wages is stronger than with noseparations. The model is estimated structurally using Spanish data forthe period 1985-1996. The main finding is that, although the decrease inreservation wages is the main determinant of the change in the exit ratefrom unemployment for the first four months, later on the only effect comesfrom the job offer arrival rate, given that acceptance probabilities areroughly equal to one.

Unemployment insurance with endogenous search intensity and precautionary saving

A welfare analysis of unemployment insurance (UI) is performed in a generalequilibrium job search model. Finitely-lived, risk-averse workers smooth consumption over time by accumulating assets, choose search effort whenunemployed, and suffer disutility from work. Firms hire workers, purchasecapital, and pay taxes to finance worker benefits; their equity is the assetaccumulated by workers. A matching function relates unemployment, hiringexpenditure, and search effort to the formation of jobs. The model is calibrated to US data; the parameters relating job search effort to the probability of job finding are chosen to match microeconomic studies ofunemployment spells. Under logarithmic utility, numerical simulation shows rather small welfaregains from UI. Even without UI, workers smooth consumption effectivelythrough asset accumulation. Greater risk aversion leads to substantiallylarger welfare gains from UI; however, even in this case much of its welfareimpact is due not to consumption smoothing effects, but rather to decreased work disutility, or to a variety of externalities.

Job search and asset accumulation under borrowing constraints

In this paper I show how borrowing constraints and job search interact.I fit a dynamic model to data from the National Longitudinal Survey(1979-cohort) and show that borrowing constraints are significant. Agentswith more initial assets and more access to credit attain higher wagesfor several periods after high school graduation. The unemployed maintaintheir consumption by running down their assets, while the employed saveto buffer against future unemployment spells. I also show that, unlikein models with exogenous income streams, unemployment transfers, byallowing agents to attain higher wages do not 'crowd out' but increasesaving.

Individual Strategies for Different Learners

Aquest treball fa un repàs a les diferents teories relacionades amb el camp d’estudi de les estratègies d’aprenentatge de segones llengües i respon a preguntes de recerca relacionades amb la freqüència d’ús de les estratègies i la relació amb les diferències individuals. La primera part és una introducció on s’hi plantegen les preguntes de recerca en les quals es basa el treball. La segona part, consisteix en un resum de les teories relacionades amb el tema de les estratègies d’estudi de segones llengües, i una posada en comú d’aquestes per mostrar les dificultats que hi ha per trobar consens en quant a la identificació i classificació de les estratègies. La tercera part, presenta la metodologia utilitzada per a la recollida de dades per tal de contestar les preguntes de recerca. En la quarta part es desenvolupa la recerca duta a terme; i finalment es presenten les conclusions extretes de cada pregunta de recerca plantejada.

En route to a more democratic European Union – An analysis of the communication strategies of European Citizens’ Initiatives (ECIs)

L’èxit de l’iniciativa ciutadana europea (ICE) com a instrument de democràcia directa a nivell europeu està directament relacionat amb la seva promulgació. Els ciutadans d’arreu Europa han d’estar informats sobre aquest nou mecanisme per tal que es dugui a terme, la qual cosa suposa una dificultat. Aquest estudi qualitatiu ens mostra els recursos i problemes en la divulgació de les ICE. Una anàlisi basat en entrevistes amb diferents organitzadors d’aquestes ICE que ens dona algunes idees sobre les seves estratègies de comunicació, així com l’ús d’eines de comunicació i relacions amb els mitjans de comunicació. A banda de les dificultats lingüístiques i financeres hi ha altres obstacles més específics relacionats amb l’ICE.

A search for microquasar candidates at low galactic latitudes

Recent studies of relativistic jet sources in the Galaxy, also known as microquasars, have been very useful in trying to understand the accretion/ejection processes that take place near compact objects. However, the number of sources involved in such studies is still small. In an attempt to increase the number of known microquasars we have carried out a search for new Radio Emitting X-ray Binaries (REXBs). These sources are the ones to be observed later with VLBI techniques to unveil their possible microquasar nature. To this end, we have performed a cross-identification between the X-ray ROSAT all sky survey Bright Source Catalog (RBSC) and the radio NRAO VLA Sky Survey (NVSS) catalogs under very restrictive selection criteria for sources with |b|<5 degrees. We have also conducted a deep observational radio and optical study for six of the selected candidates. At the end of this process two of the candidates appear to be promising, and deserve additional observations aimed to confirm their proposed microquasar nature.

Search for very high energy gamma-ray emission from pulsar-pulsar wind nebula systems with the MAGIC telescope

The MAGIC collaboration has searched for high-energy gamma-ray emission of some of the most promising pulsar candidates above an energy threshold of 50 GeV, an energy not reachable up to now by other ground-based instruments. Neither pulsed nor steady gamma-ray emission has been observed at energies of 100 GeV from the classical radio pulsars PSR J0205+6449 and PSR J2229+6114 (and their nebulae 3C58 and Boomerang, respectively) and the millisecond pulsar PSR J0218+4232. Here, we present the flux upper limits for these sources and discuss their implications in the context of current model predictions.

The so-called "Spanish model" - Tobacco industry strategies and its impact in Europe and Latin America

Background To demonstrate the tobacco industry rationale behind the "Spanish model" on non-smokers' protection in hospitality venues and the impact it had on some European and Latin American countries between 2006 and 2011. Methods Tobacco industry documents research triangulated against news and media reports. Results As an alternative to the successful implementation of 100% smoke-free policies, several European and Latin American countries introduced partial smoking bans based on the so-called "Spanish model", a legal framework widely advocated by parts of the hospitality industry with striking similarities to "accommodation programmes" promoted by the tobacco industry in the late 1990s. These developments started with the implementation of the Spanish tobacco control law (Ley 28/2005) in 2006 and have increased since then. Conclusion The Spanish experience demonstrates that partial smoking bans often resemble tobacco industry strategies and are used to spread a failed approach on international level. Researchers, advocates and policy makers should be aware of this ineffective policy.