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Modern empirical approaches to characterize and estimate equilibrium outcomes in differentiated product markets
No full textI progressi nella letteratura di IO empirica attribuibili a Berry (1994) e Berry, Levinsohn e Pakes (1995) (noto come BLP in letteratura) hanno permesso di produrre sofisticate analisi di mercato anche partendo da dati aggregati a livello di prodotto. Questa tesi parte da questi sviluppi nella letteratura e produce un'analisi separata della struttura del mercato italiano delle automobili e di quella del mercato irlandese delle bevande gassate. Entrambi i mercati s ono o ligopolistici ed il prodotto e ' differenziato. L'innovazione dei risultati proposti e ' stata resa possibile grazie all'uso di dati particolarmente originali. Per quanto riguarda il mercato italiano delle automobili si è costruita, per il periodo 1989-2000, una base d ati e ombinando i nformazioni a 1 ivello d i p rodotto ( per 1 e q uali s i r ingrazia F iat S .p.A. e d Editoriale Domus Quattroruote) con informazioni a livello di individui (ricavata da una sezione speciale dell'indagine della Banca d'Italia sui bilanci delle famiglie). I dati sono stati inizialmente utilizzati per identificare la differenza nelle distribuzioni delle caratteristiche degli individui che comprano un veicolo nuovo rispetto a coloro che preferiscono non comperarlo (vista come scelta alternativa). L'identificazione di diverse distribuzioni di caratteristiche nei gruppi di individui acquirenti e non acquirenti, resa possibile grazie ai nostri dati, ci ha permesso di guadagnare efficienza nelle stime e di stimare elasticità di sostituzione di prezzo più' verosimili. I nostri dati mostrano che modelli tipo BLP basati su informazioni esogene sulle caratteristiche di un'unica popolazione producono elasticità di sostituzione di prezzo sovrastimate fino ad un 30%. La stessa base dati e' stata poi utilizzata per valutare l'effetto prodotto, in termini di concorrenza sul mercato, dagli incentivi alla rottamazione (adottati in Italia nel periodo 1997-2000). I nostri risultati mostrano che la politica degli incentivi ha portato competizione nel mercato: i prezzi, per solo effetto degli incentivi, si sono ridotti di un 8% nel 1998 e di un 10% nel 2000. Il livello di competizione non ha interessato allo stesso modo le diverse case madri: le case madri aventi nel loro portafoglio di produzione anche piccole automobili sono state quelle maggiormente danneggiate.
Un'altra base dati originale e' stata utilizzata per il mercato irlandese delle bevande gassate. La base dati copre il periodo giugno/luglio 1992 - aprile maggio 1997 e consiste in dati bimensili a livello di prodotto con ricche informazioni sulla distribuzione (informazioni della copertura di negozi da parte di ogni singola marca di prodotto). La copertura dei negozi viene interpretata come una misura di una distanza potenziale che un consumatore deve affrontare per trovare un prodotto disponibile. Questa informazione viene usata per aggregare rispetto a due tipologie di individui: il gruppo di individui che trova il prodotto nel negozio vicino ed il gruppo di individui che non lo trova. Una prima analisi ottiene come risultato che, diversamente da quanto previsto dalla letteratura sul prodotto omogeneo, non esiste una relazione positiva tra la dimensione dell'impresa (in termini di quota di mercato) e potere di mercato. La stessa analisi mette poi in luce l'importanza della copertura dei negozi nel processo di competizione. L'analisi viene poi successivamente arricchita simulando direttamente gli individui. Viene assunta che una delle caratteristiche fondamentali dei consumatori sia la loro reazione ad una presenza/assenza di un certo prodotto nel negozio a loro più vicino. I risultati mostrano come l'informazione sulla distribuzione dei prodotti risulti necessaria per una corretta identificazione del modello. Le primitive delle nostre stime vengono poi usate per mostrare che la decisione della Coca Cola di avere una distribuzione diversa per la Fanta e' una decisione ottima di lungo periodo.
This thesis uses the advancements in the literature of product differentiation developed by Berry (1994) and Berry, Levinsohn and Pakes (1995) in order to analyze, separately, the structures of the Italian automobile and the Irish carbonated soft drink markets. Simulation techniques to aggregate individuals' choices have been largely used. The novelty of the results departs from the originality of the information collected.
Regarding the Italian automobile market we set up a new dataset merging market level data (which we thank Fiat S.p.A. and Editoriale Domus Quattroruote) and microdata (from a special section of the Bank of Italy Survey of Households' Income and Wealth) for the period 1989-2000. We use this new dataset to show that, controlling for the different characteristics of individuals buying a new vehicle or preferring the outside option (not buying a new vehicle), let us to gain efficiency and estimate more reliable price elasticities of substitution. Our data show that models like BLP, based on exogenous information on a unique population, produce price elasticities of substitution that are, on average, overestimated by a 30%. The same dataset is then used to evaluate the impact, in terms of market competition, of the policy of scrap incentives adopted in Italy since 1997 to 2000. We find that, once controlled for the other characteristics, the scrap incentives induced competition in the market: prices were reduced up to 8% in 1998 and 10% in 2000. The level of competition has not been equally borne by the different parent houses. Its effect has been stronger on parent houses holding portfolios of small cars.
An original dataset has been setup also for the Irish carbonated soft drink market. The dataset consists of bimonthly market level retail scanner data (period June/July 1992 - April/May 1997) with rich information on the distribution of the products (each brand's shops coverage) collated by Irish AC Nielsen. We interpret shops coverage as a measure of a potential distance a consumer has to undertake to find available a product. We use this information to aggregate over different types of individuals. We produce a positive analysis aimed at: i) showing (contrary to the homogenous good literature) the absence of a positive relation between market size and market power; ii) stressing the relevance of the shops coverage in the process of competition. We then enrich our analysis simulating directly our individuals. We assume one of their attributes to be their reaction to the presence/absence of the products in their closest shops. We find the information on the distribution of the products to be necessary for a proper identification of our model. We use the primitives of our estimates to show the optimality of the long run decision on shops coverage
Platform competition in the tablet PC market: The effect of application quality
Full text linkThe tablet PC market is dominated by two platforms: iOS and Android. In this paper, we combine tablet-level data with data on the quality of the top 1000 mobile applications from these platforms and estimate a structural demand model. We exploit variations over three periods and five European countries to find whether the application quality affects tablet demand. We then run two counterfactuals. The first counterfactual suggests that an improvement in application quality benefits the tablet producers on that platform with a more pronounced effect on the demand for Android-based tablets. The second counterfactual discusses the policy of leveling the app quality of the two stores. It shows that such a policy favors the tablet producers adopting the lowest quality app store (Google) and stimulates the adoption of tablet PCs. This generates consumer surplus in tablet demand
Updates management in mobile applications: iTunes versus Google Play
Full text linkThis paper focuses on a specific strategy that developers of mobile applications may use to stimulate demand: The release of updates. We develop a theoretical analysis that shows that developers have incentives to release updates when experiencing a drop in performance. The predictions of the model are then tested using an unbalanced panel of top 1,000 apps iniTunes and Google Play for five European countries. We estimate that while in iTunes the release of an update stimulates a 26% increase in download growth, in Google Play updates play a less significant role. This difference is partly due to systematic differences in apps and in developers operating in the two stores (“selection effect”), and partly to a lack of quality control on apps and updates in Google Play (“quality c heck effect” ). These findings highlight the crucial importance of an appropriate management of updates as well as the relevance of institutional characteristics of the app stores
To Upgrade or Not to Upgrade? The Release of New Versions to Survive in the Hypercompetitive App Market
No full textVery low entry barriers and an exceptionally high degree of competition characterize the market for mobile applications. In such an environment one of the critical issues is how to attract the attention of users. Practitioners and developers are well aware that managing app updates (i.e., releasing new versions of an existing app) is critical to increase app visibility and to keep users engaged, disguising a hidden strategy to stimulate downloads. We use unbalanced panel data with characteristics for the top 1,000 apps on iTunes and Google Play stores, for five European countries, to empirically investigate publishers’ strategies concerning the release of updates. We find that only in the case of iTunes updates boost downloads and are more likely to be released when the app is experiencing poor performance. We interpret this finding as evidence that the lack of quality control by Google Play leads to an excess of updating of Android apps
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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