Thu, 11 Mar 2010 18:57:26 GMT RePEC DCMS Repository [10 articles] Paolo Furlani paolo.furlani@unitn.it tag:cs.unitn.it:2010-03-11.18:57:26 Copyright © 1997-2010 cs.unitn.it PF Python Atom Fabio Pieri http://repec.cs.unitn.it/People/pieri_fabio.html Enrico Zaninotto http://repec.cs.unitn.it/People/zaninotto_enrico.html

In this paper we made use of an econometric approach to efficiency analysis in order to capture the role of vertical integration and outsourcing on firm's efficiency. Vertical integration is considered an indicator of structure, while outsourcing represents the process of its change. We consider inefficiency measures as indicators of organizational heterogeneity, related to the firm's choices regarding the phases of the production process that are under its control. We find support for the hypothesis of a relationship between vertical integration and efficiency. The results on outsourcing activity, and in particular the interaction between outsourcing and vertical structure, indicate that heterogeneous patterns, far from tending to cancel out each other as a consequence of common external changes, are reinforcing. Moreover, the sensitivity of inefficiency variance to the cycle, indicate that different firms may have different dynamic properties.

2010-03-01T12:00:00-00:00 2010-03-11T07:51:15-00:00 tag:disa-wp:2010/1 Massimo Riccaboni http://repec.cs.unitn.it/People/riccaboni_massimo.html Sandro Trento http://repec.cs.unitn.it/People/trento_sandro.html Enrico Zaninotto http://repec.cs.unitn.it/People/zaninotto_enrico.html

It is quite common that public policies take as benchmark mean values of relevant policy variables (average firm size, average productivity, average income, etc.). In such a case the policy maker introduces incentives that should change individual behaviour in order to increase average values of the policy relevant variables.\x10When this kind of policies are unsuccessful it is thought that the incentives are badly designed so that the entire problem is considered as a problem of mechanism design.\x10In this paper the Authors maintain that policy makers should always take into account that incentives have an impact not only on individual behaviour but also on the distribution and law of motion of the aggregate phenomena that may be different from the sum of micro behaviours.\x10Three different cases of proportional growth phenomena (firm's size growth, income distribution and research production) are analyzed, in the paper, through simulations. Some tentative general principles for public policies are identified.

2009-11-01T12:00:00-00:00 2009-11-30T07:28:48-00:00 tag:disa-wp:2009/9 Franco Molinari http://repec.cs.unitn.it/People/molinari_franco.html

This note provides an introduction to the pricing kernel methodology for financial derivatives. In order to illustrate the pricing kernel approach we apply it to the Black and Scholes model and obtain the famous Black and Scholes formula for the fair price of an European call option.

2009-11-01T12:00:00-00:00 2010-01-26T10:24:38-00:00 tag:disa-wp:2009/8 Emanuele Taufer http://repec.cs.unitn.it/People/taufer_emanuele.html Nikolai Leonenko http://repec.cs.unitn.it/People/leonenko_nikolai.html Marco Bee http://repec.cs.unitn.it/People/bee_marco.html

Continuous-time stochastic volatility models are becoming increasingly popular in finance because of their flexibility in accommodating most stylized facts of financial time series. However, their estimation is difficult because the likelihood function does not have a closed-form expression.\x10In this paper we propose a characteristic function-based estimation method for non-Gaussian Ornstein-Uhlenbeck-based stochastic volatility models. After deriving explicit expressions of the characteristic functions for various cases of interest we analyze the asymptotic properties of the estimators and evaluate their performance by means of a simulation experiment. Finally, a real-data application shows that the superposition of two Ornstein-Uhlenbeck processes gives a good approximation to the dependence structure of the process.

2009-10-01T12:00:00-00:00 2009-12-02T16:37:52-00:00 tag:disa-wp:2009/7 Matteo Brunelli http://repec.cs.unitn.it/People/brunelli_matteo.html Mario Fedrizzi http://repec.cs.unitn.it/People/fedrizzi_mario.html Michele Fedrizzi http://repec.cs.unitn.it/People/fedrizzi_michele.html

In this paper we propose an approach to Social Network Analysis (SNA) based on fuzzy m-ary adjacency relations. In particular, we show that the dimension of the analysis can naturally be increased and interesting results can be derived. Therefore, fuzzy m-ary adjacency relations can be computed starting from fuzzy binary relations and introducing OWA-based aggregations. The behavioral assumptions derived from the measure and the exam of individual propensity to connect with other suggest that OWA operators can be considered particularly suitable in characterizing such relationships.

2009-07-01T12:00:00-00:00 2009-09-11T09:07:38-00:00 tag:disa-wp:2009/6 Michele Fedrizzi http://repec.cs.unitn.it/People/fedrizzi_michele.html Matteo Brunelli http://repec.cs.unitn.it/People/brunelli_matteo.html

In this paper we show that the widely used normalization constraint SUM(i=1,n) wi = 1 does not apply to the priority vectors associated with reciprocal relations, whenever additive transitivity is involved. We show that misleading applications of this type of normalization may lead to unsatisfactory results and we give some examples from the literature. Then, we propose an alternative normalization procedure which is compatible with additive transitivity and leads to better results.

2009-07-01T12:00:00-00:00 2009-07-29T09:27:09-00:00 tag:disa-wp:2009/5 Loris Gaio http://repec.cs.unitn.it/People/gaio_loris.html Alessandro Rossi http://repec.cs.unitn.it/People/rossi_alessandro.html Matthijs den Besten http://repec.cs.unitn.it/People/den_besten_matthijs.html Jean-Michel Dalle http://repec.cs.unitn.it/People/dalle_jean-michel.html

In the paper we investigate an organizational practice meant to increase the quality of commons-based peer production: the use of template messages in wiki collections to highlight editorial bugs and call for intervention. In the context of SimpleWiki, an online encyclopedia of the Wikipedia family, we focus on {complex}, a template which is used to flag articles disregarding the overall goals of simplicity and readability. We characterize how this template is placed on and removed from articles and we use survival analysis to study the emergence and successful treatment of these bugs in the collection.

2009-07-01T12:00:00-00:00 2009-07-29T09:23:29-00:00 tag:disa-wp:2009/4 Loris Gaio http://repec.cs.unitn.it/People/gaio_loris.html Alessandro Rossi http://repec.cs.unitn.it/People/rossi_alessandro.html Matthijs den Besten http://repec.cs.unitn.it/People/den_besten_matthijs.html Jean-Michel Dalle http://repec.cs.unitn.it/People/dalle_jean-michel.html

In this paper we investigate how in commons based peer production a large community of contributors coordinates its efforts towards the production of high quality open content. We carry out our empirical analysis at the level of articles and focus on the dynamics surrounding their production. That is, we focus on the continuous process of revision and update due to the spontaneous and largely uncoordinated sequence of contributions by a multiplicity of individuals. We argue that this loosely regulated process, according to which any user can make changes to any entry, while allowing highly creative contributions, has to come into terms with potential issues with respect to the quality and consistency of the output. In this respect, we focus on emergent, bottom up organizational practice arising within the Wikipedia community, namely the use of template messages, which seems to act as an effective and parsimonious coordination device in emphasizing quality concerns (in terms of accuracy, consistency, completeness, fragmentation, and so on) or in highlighting the existence of other particular issues which are to be addressed. We focus on the template "NPOV" which signals breaches on the fundamental policy of neutrality of Wikipedia articles and we show how and to what extent imposing such template on a page affects the production process and changes the nature and division of labor among participants. We find that intensity of editing increases immediately after the "NPOV" template appears. Moreover, articles that are treated most successfully, in the sense that "NPOV" disappears again relatively soon, are those articles which receive the attention of a limited group of editors. In this dimension at least the distribution of tasks in Wikipedia looks quite similar to what is know about the distribution in the FLOSS development process.

2009-07-01T12:00:00-00:00 2009-07-29T09:22:40-00:00 tag:disa-wp:2009/3 Laura Magazzini http://repec.cs.unitn.it/People/magazzini_laura.html Fabio Pammolli http://repec.cs.unitn.it/People/pammolli_fabio.html Massimo Riccaboni http://repec.cs.unitn.it/People/riccaboni_massimo.html Maria Alessandra Rossi http://repec.cs.unitn.it/People/rossi_maria_alessandra.html

The prominent role played by patents within the pharmaceutical domain is unquestionable. In this paper we take an unusual perspective and focus on a relatively neglected implication of patents: the effect of patent-induced information disclosure (of both successes and failures) on the dynamics of R&D and market competition. The study builds upon the combination of two large datasets, linking the information about patents to firm level data on R&D projects and their outcome.\x10Two case studies in the fields of anti-inflammatory compounds and cancer research complement our analysis. We show the important role played by patent disclosure in shaping firms technological trajectories through the possibility of reciprocal monitoring in a context of parallel research efforts, and suggest the importance of enhancing the diffusion of information concerning failures, not only to avoid wasteful duplication of innovative efforts, but also as a tool for the identification of promising research trajectories.\x10\x10This paper is the result of the "R&D competition" research project carried out jointly with Adrian Towse and Martina Garau of the Office of Health Economics, London, UK.\x10A preliminary draft of the paper has been presented to the DRUID Summer Conference 2006 (Copenhagen), and to the 11th ISS Conference (Sophia-Antipolis).

2009-06-01T12:00:00-00:00 2009-06-11T08:51:58-00:00 tag:disa-wp:2009/2 Massimo Riccaboni http://repec.cs.unitn.it/People/riccaboni_massimo.html Fabio Pammolli http://repec.cs.unitn.it/People/pammolli_fabio.html Sergey V. Buldyrev http://repec.cs.unitn.it/People/buldyrev_sergey_v.html Linda Ponta http://repec.cs.unitn.it/People/ponta_linda.html H. Eugene Stanley http://repec.cs.unitn.it/People/stanley_h_eugene.html

The relationship between the size and the variance of firm growth rates is known to follow an approximate power-law behavior σ(S) similar to S^-β(S) where S is the firm size and β(S) almost equal to 0.2 is an exponent weakly dependent on S. Here we show how a model of proportional growth which treats firms as classes composed of various number of units of variable size, can explain this size-variance dependence. In general, the model predicts that β(S) must exhibit a crossover from β(0) = 0 to β(∞) = 1/2. For a realistic set of parameters, β(S) is approximately constant and can vary in the range from 0.14 to 0.2 depending on the average number of units in the firm. We test the model with a unique industry specific database in which firm sales are given in terms of the sum of the sales of all their products. We find that the model is consistent with the empirically observed size-variance relationship.

2009-06-01T12:00:00-00:00 2009-06-11T08:51:37-00:00 tag:disa-wp:2009/1