Horizontal mergers for buyer power

Salant et al. (1983) showed in a Cournot setting that horizontal mergers are unprofitable because outsiders react by increasing their output. We show that this negative effect may be compensated by the positive effect that horizontal mergers have on the buyer power of merging firms in input markets.

To Merge or to License: Implications for Competition Policy

The optimal merger policy when efficiency gains are not merger specific but can also be achieved through licensing is derived in a differentiated goods Cournot duopoly. We show that whenever both royalties and fees are feasible instruments to license technology, mergers should not be allowed, which fits the prescription of the U.S. Horizontal Merger Guidelines. When only one instrument is feasible, however, the possibility of licensing cannot be used as a definitive argument against mergers.

Mergers in Asymmetric Stackelberg Markets

It is well known that the profitability of horizontal mergers with quantity competition is scarce. However, in an asymmetric Stackelberg market we obtain that some mergers are profitable. Our main result is that mergers among followers become profitable when the followers are inefficient enough. In this case, leaders reduce their output when followers merge and this reduction renders the merger profitable. This merger increases price and welfare is reduced.Mergers, Asymmetries, Stackelberg

Buyer power of retailers with limited selling capacity

We have two upstream firms producing each one a different good. Demands of the goods are independent, symmetric and linear. Goods are sold to consumers through retailers. The units of both goods sold by retailers cannot exceed the industry selling capacity that it is distributed symmetrically among retailers. Taking as given the industry selling capacity, when the number of retailers decreases, they become bigger in the sense that their selling capacity increases. Therefore, changing the number of retailers, we can check whether the countervailing power theory, that states that bigger retailers obtain better deals from suppliers, holds in our model. We obtain that the lower the number of retailers, the lower the wholesale prices, only when the industry selling capacity is high.I acknowledge financial support from the Spanish Ministerio de Economía y Competitividad and FEDER funds ECO2015-65820-P (MINECO/FEDER) and from Generalitat Valenciana grant PROMETEO/2019/037

Divisionalization with asymmetric production costs

We study a standard duopoly model of simultaneous divisionalization and Cournot competition, assuming that firms have different marginal costs and divisions are costless. We obtain that in equilibrium only the divisions of the efficient firm are active because price is equal to the marginal cost of the inefficient firm. In the sequential case, however, this “entry-deterrence” strategy is only profitable for the efficient firm when its cost advantage is important enough. So in our setting, both firms coexist in equilibrium only when the cost difference is small enough and divisions are chosen sequentially.Financial support from the Spanish Ministry of Economic Competitiveness (PID2019-107081GB-I00), and Generalitat Valenciana (Research Project Groups 3/086, Prometeo/2021/073) is gratefully acknowledged

Survival analysis issues with interval-censored data

L'anàlisi de la supervivència s'utilitza en diversos àmbits per tal d'analitzar dades que mesuren el temps transcorregut entre dos successos. També s'anomena anàlisi de la història dels esdeveniments, anàlisi de temps de vida, anàlisi de fiabilitat o anàlisi del temps fins a l'esdeveniment. Una de les dificultats que té aquesta àrea de l'estadística és la presència de dades censurades. El temps de vida d'un individu és censurat quan només és possible mesurar-lo de manera parcial o inexacta. Hi ha diverses circumstàncies que donen lloc a diversos tipus de censura. La censura en un interval fa referència a una situació on el succés d'interès no es pot observar directament i només tenim coneixement que ha tingut lloc en un interval de temps aleatori. Aquest tipus de censura ha generat molta recerca en els darrers anys i usualment té lloc en estudis on els individus són inspeccionats o observats de manera intermitent. En aquesta situació només tenim coneixement que el temps de vida de l'individu es troba entre dos temps d'inspecció consecutius.Aquesta tesi doctoral es divideix en dues parts que tracten dues qüestions importants que fan referència a dades amb censura en un interval. La primera part la formen els capítols 2 i 3 els quals tracten sobre condicions formals que asseguren que la versemblança simplificada pot ser utilitzada en l'estimació de la distribució del temps de vida. La segona part la formen els capítols 4 i 5 que es dediquen a l'estudi de procediments estadístics pel problema de k mostres. El treball que reproduïm conté diversos materials que ja s'han publicat o ja s'han presentat per ser considerats com objecte de publicació.En el capítol 1 introduïm la notació bàsica que s'utilitza en la tesi doctoral. També fem una descripció de l'enfocament no paramètric en l'estimació de la funció de distribució del temps de vida. Peto (1973) i Turnbull (1976) van ser els primers autors que van proposar un mètode d'estimació basat en la versió simplificada de la funció de versemblança. Altres autors han estudiat la unicitat de la solució obtinguda en aquest mètode (Gentleman i Geyer, 1994) o han millorat el mètode amb noves propostes (Wellner i Zhan, 1997).El capítol 2 reprodueix l'article d'Oller et al. (2004). Demostrem l'equivalència entre les diferents caracteritzacions de censura no informativa que podem trobar a la bibliografia i definim una condició de suma constant anàloga a l'obtinguda en el context de censura per la dreta. També demostrem que si la condició de no informació o la condició de suma constant són certes, la versemblança simplificada es pot utilitzar per obtenir l'estimador de màxima versemblança no paramètric (NPMLE) de la funció de distribució del temps de vida. Finalment, caracteritzem la propietat de suma constant d'acord amb diversos tipus de censura. En el capítol 3 estudiem quina relació té la propietat de suma constant en la identificació de la distribució del temps de vida. Demostrem que la distribució del temps de vida no és identificable fora de la classe dels models de suma constant. També demostrem que la probabilitat del temps de vida en cadascun dels intervals observables és identificable dins la classe dels models de suma constant. Tots aquests conceptes elsil·lustrem amb diversos exemples.El capítol 4 s'ha publicat parcialment en l'article de revisió metodològica de Gómez et al. (2004). Proporciona una visió general d'aquelles tècniques que s'han aplicat en el problema no paramètric de comparació de dues o més mostres amb dades censurades en un interval. També hem desenvolupat algunes rutines amb S-Plus que implementen la versió permutacional del tests de Wilcoxon, Logrank i de la t de Student per a dades censurades en un interval (Fay and Shih, 1998). Aquesta part de la tesi doctoral es complementa en el capítol 5 amb diverses propostes d'extensió del test de Jonckeere. Amb l'objectiu de provar una tendència en el problema de k mostres, Abel (1986) va realitzar una de les poques generalitzacions del test de Jonckheere per a dades censurades en un interval. Nosaltres proposem altres generalitzacions d'acord amb els resultats presentats en el capítol 4. Utilitzem enfocaments permutacionals i de Monte Carlo. Proporcionem programes informàtics per a cada proposta i realitzem un estudi de simulació per tal de comparar la potència de cada proposta sota diferents models paramètrics i supòsits de tendència. Com a motivació de la metodologia, en els dos capítols s'analitza un conjunt de dades d'un estudi sobre els beneficis de la zidovudina en pacients en els primers estadis de la infecció del virus VIH (Volberding et al., 1995).Finalment, el capítol 6 resumeix els resultats i destaca aquells aspectes que s'han de completar en el futur.Survival analysis is used in various fields for analyzing data involving the duration between two events. It is also known as event history analysis, lifetime data analysis, reliability analysis or time to event analysis. One of the difficulties which arise in this area is the presence of censored data. The lifetime of an individual is censored when it cannot be exactly measured but partial information is available. Different circumstances can produce different types of censoring. Interval censoring refers to the situation when the event of interest cannot be directly observed and it is only known to have occurred during a random interval of time. This kind of censoring has produced a lot of work in the last years and typically occurs for individuals in a study being inspected or observed intermittently, so that an individual's lifetime is known only to lie between two successive observation times.This PhD thesis is divided into two parts which handle two important issues of interval censored data. The first part is composed by Chapter 2 and Chapter 3 and it is about formal conditions which allow estimation of the lifetime distribution to be based on a well known simplified likelihood. The second part is composed by Chapter 4 and Chapter 5 and it is devoted to the study of test procedures for the k-sample problem. The present work reproduces several material which has already been published or has been already submitted.In Chapter 1 we give the basic notation used in this PhD thesis. We also describe the nonparametric approach to estimate the distribution function of the lifetime variable. Peto (1973) and Turnbull (1976) were the first authors to propose an estimation method which is based on a simplified version of the likelihood function. Other authors have studied the uniqueness of the solution given by this method (Gentleman and Geyer, 1994) or have improved it with new proposals (Wellner and Zhan, 1997).Chapter 2 reproduces the paper of Oller et al. (2004). We prove the equivalence between different characterizations of noninformative censoring appeared in the literature and we define an analogous constant-sum condition to the one derived in the context of right censoring. We prove as well that when the noninformative condition or the constant-sum condition holds, the simplified likelihood can be used to obtain the nonparametric maximum likelihood estimator (NPMLE) of the failure time distribution function. Finally, we characterize the constant-sum property according to different types of censoring. In Chapter 3 we study the relevance of the constant-sum property in the identifiability of the lifetime distribution. We show that the lifetime distribution is not identifiable outside the class of constant-sum models. We also show that the lifetime probabilities assigned to the observable intervals are identifiable inside the class of constant-sum models. We illustrate all these notions with several examples.Chapter 4 has partially been published in the survey paper of Gómez et al. (2004). It gives a general view of those procedures which have been applied in the nonparametric problem of the comparison of two or more interval-censored samples. We also develop some S-Plus routines which implement the permutational version of the Wilcoxon test, the Logrank test and the t-test for interval censored data (Fay and Shih, 1998). This part of the PhD thesis is completed in Chapter 5 by different proposals of extension of the Jonckeere's test. In order to test for an increasing trend in the k-sample problem, Abel (1986) gives one of the few generalizations of the Jonckheree's test for interval-censored data. We also suggest different Jonckheere-type tests according to the tests presented in Chapter 4. We use permutational and Monte Carlo approaches. We give computer programs for each proposal and perform a simulation study in order compare the power of each proposal under different parametric assumptions and different alternatives. We motivate both chapters with the analysis of a set of data from a study of the benefits of zidovudine in patients in the early stages of the HIV infection (Volberding et al., 1995).Finally, Chapter 6 summarizes results and address those aspects which remain to be completed

Income, distance and spatial effects in the Monocentric model. The Barcelona Metropolitan Area case.

This paper focuses on the income distribution of households in Barcelona Metropolitan Area. For this purpose we use the Monocentric model. As the basic model does not have direct implications for this distribution, we survey the extensions of the model that have been used in empirical literature. One of the most promising ways is to introduce externalities in the decision process; they can result directly from exogenous amenities (natural traits of urban area) or be created directly by other agents’ decisions. In this case, a spatial lag model and spatial error model are suited for the empirical purposes. We present evidence that any model with spatial effects improves significantly the econometric results.

Welfare effects of downstream mergers and upstream market concentration

We consider a dominant upstream firm selling an input to several downstream firms through observable, non-discriminatory two-part tariff contracts. Downstream firms can alternatively buy the input from a less efficient source of supply. In this setting, we analyze the relationship between the competitive effects of downstream mergers and the level of concentration at the upstream level. We show that a downstream merger leads to lower wholesale prices. This translates into lower final prices only when the upstream market is sufficiently concentrated. In this case, a downstream merger tends to be both procompetitive and profitable.Financial support from Ministerio de Ciencia e Innovación and FEDER funds under project SEJ 2007-62656, from Spanish Ministerio de Economía y Competitividad under project ECO2012-34928 and the IVIE is gratefully acknowledged

Fee versus royalty licensing in a Cournot duopoly with increasing marginal costs

We consider a symmetric homogeneous Cournot duopoly operating under increasing marginal costs. One of the firms owns a patented superior technology that reduces the intercept of the marginal cost function. We compare the incentives of the insider patentee to license the technology to the rival firm either through a fixed fee or through a royalty. We obtain that royalty licensing does not necessarily dominates in our setting: when decreasing returns are important, a royalty is superior only for small enough innovations, whereas a fixed fee is chosen for large innovations. Aditionally, we show that our model is able to replicate the results in Wang (2002), which analyzes the same question in a differentiated duopoly with constant marginal costs.Financial support from the Spanish Ministry of Economic Competitiveness (PID2019-107081GB-I00), and Generalitat Valenciana (Research Project Groups 3/086, Prometeo/2021/073) is gratefully acknowledged