The stability of simulation based estimation of the multiperiod multinominal probit model with individual specific covariates

The multi-period multinomial Probit model (MMPM) is seen as a flexible tool to explain individual choices among several alternatives over time. There are two versions of this model: a) for each individual the covariates for all alternatives are known and b) for each individual only the parameters of the alternative which was chosen is known. The main difficulty with the MMPM was the calculation of the probability for the individual sequence of chosen alternatives, which requires the computation of the integral over a high dimensional multivariate Normal density. This remedy was removed by the Smooth Recursive Conditional (SRC) simulator. Several simulation studies have investigated the stability of the MMPM estimates with special emphasis to the number of replications of the SRC routine. In contrast to these studies, which use the case of alternative specific covariates, we use the case of the individual specific covariates. We conclude that the MMPM with individual specific covariates is only weakly identified, generalizing Keane's (1992) result for the one period case. As a consequence the maximization of the simulated likelihood often converges to a singular covariance structure so that the SRC-routine stops iterating. This feature cannot be avoided by increasing the number of replications in the SRC-routine. The percentage of these failures rapidly increases with the number of alternatives. --discrete choice models,multi-period multinomial,probit models,simulated maximum likelihood method,smooth recursive conditional simulator,panel data

The stability of simulation based estimation of the multiperiod multinominal probit model with individual specific covariates

The multi-period multinomial Probit model (MMPM) is seen as a flexible tool to explain individual choices among several alternatives over time. There are two versions of this model: a) for each individual the covariates for all alternatives are known and b) for each individual only the parameters of the alternative which was chosen is known. The main difficulty with the MMPM was the calculation of the probability for the individual sequence of chosen alternatives, which requires the computation of the integral over a high dimensional multivariate Normal density. This remedy was removed by the Smooth Recursive Conditional (SRC) simulator. Several simulation studies have investigated the stability of the MMPM estimates with special emphasis to the number of replications of the SRC routine. In contrast to these studies, which use the case of alternative specific covariates, we use the case of the individual specific covariates. We conclude that the MMPM with individual specific covariates is only weakly identified, generalizing Keane’s (1992) result for the one period case. As a consequence the maximization of the simulated likelihood often converges to a singular covariance structure so that the SRC-routine stops iterating. This feature cannot be avoided by increasing the number of replications in the SRC-routine. The percentage of these failures rapidly increases with the number of alternatives

Sozialabgaben und Beschäftigung (Social security contributions and employment)

"The relationship between high social security contributions and the local labour market performance has been and still is intensively discussed in the political arena. Various reform concepts suggested by members of politics and associations are going around. Some measures to restrict the increase in social security contributions have been implemented over the past years. To evaluate the different reform approaches, the causal relationship between social security contributions and employment is of significant importance. The question at the crux of this issue is what effects a change/reduction in the social security contribution rates has on firstly, labour supply and demand alone, and then, when taking into consideration circular-flow effects, on the employment level in the economy as a whole. The analyses of supply and demand show that by reducing social security contributions ceteris paribus additional manpower can be motivated to take up employment, and that companies would be prepared to hire additional workers. This is also true at macroeconomic level. Without counter-financing, the circular-flow model predicts a permanent increase in labour demand, and thus in employment, by 150,000 to 160,000 people in the case of a linear reduction in social security contributions by one percentage point. Considerably lower or even slightly negative employment effects result from counter-financing with direct or indirect taxes or a combination thereof. If the reduction in social security contributions is carried out in an asymmetrical way, for example by means of a tax-free allowance, this results in considerably higher labour market effects than with a linear reduction with an identical volume of financial relief. In order to really be able to realise the additional employment opportunities of low-skilled and low-wage workers provided by an asymmetrical reduction in social security contributions, it would also be important when developing supporting wage policies, for tax increases which also affect low-income groups not to result in a disproportionately large increase in the lower wage groups. This concluding finding shows again the importance of a close co-operation between fiscal policy and collective bargaining policy." (Author's abstract, IAB-Doku) ((en))Sozialabgaben, Beschäftigungseffekte, Arbeitskräfteangebot, Arbeitskräftenachfrage

Das Kotti-Prinzip : urbane Komplizenschaften zwischen Räumen, Menschen, Zeit, Wissen und Dingen

http://ruby-press.com/book-launch-and-discussion-das-kotti-prinzip-urbane-komplizenschaften-zwischen-raumen-menschen-zeit-wissen-und-dingen/The publication consists of 2 parts: A large-format booklet with axonometric drawings introduces the visible and invisible accomplices of Kotti & Co. The detailed mappings show how actors, places and actions work together over long periods of time and how complex “interfering from below” is in urban development policy processes. It’s about making the strategies and tactics of Kotti & Co understandable so that they can become a model for others. This visual analysis is supplemented by a smaller booklet containing a series of essays, that shed light on the power of civil society and academic engagement for urban development.Die Publikation besteht aus 2 Teilen: Ein großformatiges Heft mit doppelseitigen axonometrischen Zeichnungen stellt die sichtbaren und unsichtbaren Kompliz*innen von Kotti & Co vor. Die anschaulichen Übersichten zeigen, wie Akteure, Orte und Handlungen über längere Zeiträume zusammenwirken und wie vielschichtig sich das „Einmischen von unten“ in stadtentwicklungspolitische Prozesse gestaltet. Es geht darum, die Strategien und Taktiken von Kotti & Co nachvollziehbar zu machen, damit sie zum Modell für andere werden. Ergänzt wird diese visuelle Analyse durch einen Textband, der in einer Reihe von Essays Handlungsmöglichkeiten im Spannungsfeld von zivilgesellschaftlichem und akademischem Engagement beleuchtet.Wem gehört die Stadt? Wer darf wohnen – wer muss gehen? Wer entscheidet darüber? Und mit welchen Mitteln? Ein halbes Jahr lang begleiteten Christine Bock und Ulrich Pappenberger die Mieter*inneninitiative Kotti & Co um zu verstehen, wie Sozialmieter*innen zu einflussreichen Akteuren der Berliner Stadt- und Wohnungspolitik wurden. Die Studie folgt der Akteur-Netzwerk-Theorie und erzählt von der Macht des Kollektivs. Sie beleuchtet anhand von Mappings, wie sich Räume, Menschen, Zeit, Wissen und Dinge zu Kompliz*innen eines wirkungsvollen Akteur-Netzwerk verbinden.Who owns the city? Who is allowed to stay – who has to go? Who decides about it? And by what means? For about six months, Christine Bock and Ulrich Pappenberger accompanied the tenant initiative Kotti & Co to understand how tenants had become influential actors affecting Berlin’s city and housing politics. The study employs an actor-network theory approach in order to talk about the power of the collective. By means of mappings, it sheds light on how spaces, people, time, knowledge and things connect as accomplices of an effective actor-network.TU Berlin, Open-Access-Mittel - 201

Foerderung eines Niedriglohnsektors Die Diagnose stimmt, die Therapie noch nicht

In der 'Benchmarking-Gruppe' des Buendnisses fuer Arbeit werden verschiedene Varianten eines gestaffelten Zuschusses zu den Sozialversicherungsbeitraegen diskutiert. Nach dem Vorschlag der Friedrich-Ebert-Stiftung sollen bei Vollzeit die Sozialabgaben bis zu einem Monatslohn von 1500 DM ganz, bis 3000 DM teilweise vom Staat uebernommen werden. Diese Bezuschussung niedriger Loehne entlastet einerseits die Betriebe von Arbeitskosten und stockt andererseits die Nettoeinkommen der Arbeitnehmer auf. In dem Bericht werden die Finanzierungswirkungen der Zuschuesse im Kreislaufzusammenhang und die vermuteten Beschaeftigungseffekte berechnet. Es wird festgestellt, dass die 'Einfuehrungskosten' hoch und die zusaetzlichen Beschaeftigungseffekte bescheiden sind. Ausserdem birgt die Ausgestaltung des Vorschlags die Gefahr des Missbrauchs. (IAB)SIGLEAvailable from IAB / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Radiotherapy of Breast Cancer in Laterally Tilted Prone vs. Supine Position: What about the Internal Mammary Chain?

Background: In the multimodal breast-conserving curative therapy of some high-risk breast cancer patients, extended external beam radiotherapy (EBRT) not only to the breast but also to the supraclavicular fossa and the internal mammary chain (parasternal region (PSR)) is indicated. We report a dosimetric study on the EBRT of the breast (“B”) and the breast including PSR (“B + PSR”), comparing the supine and the laterally tilted prone patient positions in free breathing. Methods: The planning CT scans of 20 left- and 20 right-sided patients were analyzed. EBRT plans were calculated with 3D conformal EBRT (3D) and with intensity-modulated EBRT (IMRT) for “B” and “B + PSR” in the prone and supine positions. The mean and threshold doses were computed. The quality of EBRT plans was compared with an overall plan assessment factor (OPAF), comprising three subfactors, homogeneity, conformity, and radiogenic exposure of OAR. Results: In the EBRT of “B”, prone positioning significantly reduced the exposure of the OARs “heart” and “ipsilateral lung” and “lymphatic regions”. The OPAF was significantly better in the prone position, regardless of the planning technique or the treated breast side. In the EBRT of “B + PSR”, supine positioning significantly reduced the OAR “heart” exposure but increased the dose to the OARs “ipsilateral lung” and “lymphatic regions”. There were no significant differences for the OPAF, independent of the irradiated breast side. Only the IMRT planning technique increased the chance of a comparatively good EBRT plan. Conclusion: Free breathing prone positioning significantly improves plan quality in the EBRT of the breast but not in the EBRT of the breast + PSR

Radiotherapy of Breast Cancer in Laterally Tilted Prone vs. Supine Position: What about the Internal Mammary Chain?

Background: In the multimodal breast-conserving curative therapy of some high-risk breast cancer patients, extended external beam radiotherapy (EBRT) not only to the breast but also to the supraclavicular fossa and the internal mammary chain (parasternal region (PSR)) is indicated. We report a dosimetric study on the EBRT of the breast (“B”) and the breast including PSR (“B + PSR”), comparing the supine and the laterally tilted prone patient positions in free breathing. Methods: The planning CT scans of 20 left- and 20 right-sided patients were analyzed. EBRT plans were calculated with 3D conformal EBRT (3D) and with intensity-modulated EBRT (IMRT) for “B” and “B + PSR” in the prone and supine positions. The mean and threshold doses were computed. The quality of EBRT plans was compared with an overall plan assessment factor (OPAF), comprising three subfactors, homogeneity, conformity, and radiogenic exposure of OAR. Results: In the EBRT of “B”, prone positioning significantly reduced the exposure of the OARs “heart” and “ipsilateral lung” and “lymphatic regions”. The OPAF was significantly better in the prone position, regardless of the planning technique or the treated breast side. In the EBRT of “B + PSR”, supine positioning significantly reduced the OAR “heart” exposure but increased the dose to the OARs “ipsilateral lung” and “lymphatic regions”. There were no significant differences for the OPAF, independent of the irradiated breast side. Only the IMRT planning technique increased the chance of a comparatively good EBRT plan. Conclusion: Free breathing prone positioning significantly improves plan quality in the EBRT of the breast but not in the EBRT of the breast + PSR