Filling the Gaps: Vacancy Chains and Agent-Based Models

Vacancy-chain analysis (VCA), a method for tracing the flows of resources such as jobs or housing, has faded from scholarly attention. This is unfortunate, because VCA is often superior to markets, auctions, or games, the more popular metaphors-cum-models of resource allocation. This paper aims to revive VCA by casting it in terms of agent-based models (ABMs). I first review and note the limitations of the Markov-chain version VCA (or MC-VCA), and then introduce an agent-based approach to vacancy chain systems, the ABM-VCA, which features the innovation of treating both resources/positions and opportunities as agents. I show that ABM-VCA can replicate MC-VCA (since the former is an MCMC estimator of the latter) and then illustrate the usefulness of ABM-VCA to empirically study off-equilibrium dynamics by using it to assessing the impact of social revolution on the judiciary of a post-socialist country. I conclude by noting the methodological possibilities opened up by ABM-VCA, such as the potential to simulating fields and ecologies. A Python implementation of ABM-VCA is available at https://github.com/r-parvulescu/abm-vca.

Jobs and Matches: Quits, Replacement Hiring, and Vacancy Chains and Vacancy Chains

In the canonical DMP model of job openings, all job openings stem from new job creation. Jobs denote worker-firm matches, which are destroyed following worker quits. Yet, employers classify 56 percent of vacancies as quit-driven replacement hiring into old jobs, which evidently outlived their previous matches. Accordingly, aggregate and firm-level hiring tightly track quits. We augment the DMP model with longer-lived jobs arising from sunk job creation costs and replacement hiring. Quits trigger vacancies, which beget vacancies through replacement hiring. This vacancy chain can raise total job openings and net employment. The procyclicality of quits can thereby amplify business cycles. (JEL E24, E32, J23, J31, J63)

The ASHA model: An alternative to the Markovian approach to housing vacancy chains: An application to the study of population in Lille (Nord, France)

This article proposes an alternative method to Markovian approaches through the housing systems analysis (ASHA) model. Its objective is to simulate the impact of the housing stock on population redistribution at a given scale and duration, by modelling the processes whereby residential mobilities are linked, initiated either by a change in the housing stock, or by a movement of housing releases that does not lead to a dwelling being occupied within the study area. The model takes into account the mobilities specific to each household category, in terms – for example – of social position, age, size or the dwelling occupied. It provides information on trends in the population structures of the different housing types brought about by vacancies-reoccupancies. The article begins by describing the model’s theoretical foundations (filtering process and housing vacancy chains) and conception. It then goes on to present, through the example of the city of Lille (Nord, France), a method of data classification that allows comparative analysis suited to the application of the ASHA model. Next, it illustrates the model’s analytical scope and the way it can be used to understand the organisation of a housing system. Finally, drawing on a number of examples (family accommodation, gentrification, housing programmes), it sets out the model’s operational utility and the way local managers can use it to understand and anticipate the impact of housing policy on the urban population.

Vacancy chains and the business cycle. Stringing together job-to-job transitions in micro data

Purpose – The purpose of this paper is to examine the dynamics of labour market flows over the business cycle through a vacancy chain model. It provides a direct computation of vacancy chains using micro data, empirically investigates the relationship between chain length and the characteristics of jobs and workers initiating the chain, and finally assesses the wage progression of workers moving along the chain. Design/methodology/approach – The paper draws on a longitudinal matched employer-employee database covering all employees in manufacturing in a large region of Italy. A transparent algorithm for vacancy chain computation is developed and standard econometric techniques are employed to analyze job-to-job transitions within identified chains. Findings – Vacancy chains account on average for more than one-third of total hires, and both the number and the length of chains are clearly pro-cyclical. Chains set in motion by women workers, young, old, blue collars, or employed by small firms tend to be shorter. There is a well-defined wage progression from the tail to the head of the chain, revealing that workers are sorted along chains according to skill and/or bargaining power. Research limitations/implications – There is a limited possibility of identifying separately individual ability and bargaining power. Practical implications – The vacancy chain methodology can increase the ability of policy makers to produce detailed maps of the labour market and identify worker profiles associated with poor outcomes and hence deserving special attention. Originality/value – For the first time, this paper operationalizes the vacancy chain approach on a large scale, at a very high level of detail, and over a long-time span.

Charge-Induced Defect Formation in LixCoO2 Battery Cathodes: XRD and PA Spectroscopy Study

Lithium-ion batteries have developed into most advanced battery systems, e.g. laptops and mobile phones. LiCoO2 is a typical intercalation battery cathode material. However, reversible charge-discharge cycling of LiCoO2 is only possible down to 50% of the available Li-ions since further removal of Li-ions drastically reduces the capacity and cycle stability. The formation of vacancy-type defects during the charging process in LixCoO2 battery cathodes was investigated by XRD and position life-time spectroscopy and Doppler broadening of positron-electron annihilation (PA) radiation as defect specific techniques [1]. Li+-extraction, which in a battery mode corresponds to charging, was performed at 293 K under electrochemical control in a 3-electrode test-cell with a Maccor Series 4000 battery tester. The composition of the lithium-ion electrode material used was: 88wt.% LiCoO2 particles, 7 wt.% carbon black as conducting agent, 5 wt.% binder material (polyvinylidene difluoride hexafluoropropylene copolymer). Structural analysis of the electrode samples was performed by means of X-Ray diffraction using a Bruker D8 Advance diffractometer in Bragg-Brentano geometry with Cu-Kα radiation. Diffractograms were measured in the 2-Theta angle range from 150to 1300and were analysed by Rietveld refinement with the programs FULLPROF [2] and X'PertHighScorePlus (Panalytical). For positron annihilation measurements a positron source (22NaCl) was sandwiched between two identical LiCoO2 electrode samples. Positron lifetime measurements were performed with a fast-fast spectrometer with a time resolution of 221 ps. The spectra were analysed by using the program pfposfit [3]. Doppler broadening (DB) measurements were performed in a coincidence setup with two high purity Ge detectors.with energy resolution for the 511 keV annihilation γ-line in the detector system corresponds to ca. 0.88keV (FWHM). Both the Doppler broadening S parameter as well as the positron lifetime component τ1 exhibit a characteristic variation with increasing amount of Li+-extraction; the S-parameter and τ1 first increases upon decreasing x from 1 to 0.6. Further Li+-extraction causes a decrease of S and τ1 (x = 0.55), followed by a re-increase for x<0.55. Conclusions: The regime of reversible charging is dominated by vacancy-type defects on the Li+-sublattice the size of which increases with increasing Li+-extraction. Indication is found that Li+-reordering which occurs at the limit of reversible Li+-extraction (x = 0.55) causes a transition from the two-dimensional agglomerates into one-dimensional vacancy chains. Degradation upon further Li+-extraction is accompanied by the formation of vacancy complexes on the Co- and anion sublattice.