43 research outputs found
Common ownership, market power, and innovation
examine the effects of overlapping ownership on market power when there are external
effects across firms. This is done in an oligopoly model with cost-reducing innovation with
technological spillovers where firms have an overlapping ownership structure based largely
on LĂłpez and Vives (2019). The model allows for Cournot competition with homogeneous
product and for Bertrand with differentiated products as well as for strategic effects of
R&D investment. It derives positive testable implications and normative results to inform
polic
Market power and welfare in asymmetric divisible good auctions
We analyze a divisible good uniform-price auction that features two groups, each with a finite number of identical bidders, who compete in demand schedules. In the linear-quadratic-normal framework, this paper presents conditions under which the unique equilibrium in linear demands exists and derives novel comparative statics results that highlight the interaction between payoff and information parameters with asymmetric groups. We find that the strategic complementarity in the slopes of traders' demands is reinforced by inference effects from prices, and we display the role of payoff and information asymmetries in explaining deadweight losses. Furthermore, price impact and the deadweight loss need not move together, and market integration may reduce welfare. The results are consistent with the available empirical evidence
General equilibrium oligopoly and ownership structure
We develop a tractable general equilibrium framework in which firms are large and have market power with respect to both products and labor, and in which a firm's decisions are affected by its ownership structure. We characterize the CournotâWalras equilibrium of an economy where each firm maximizes a shareâweighted average of shareholder utilitiesârendering the equilibrium independent of price normalization. In a oneâsector economy, if returns to scale are nonâincreasing, then an increase in âeffectiveâ market concentration (which accounts for common ownership) leads to declines in employment, real wages, and the labor share. Yet when there are multiple sectors, due to an intersectoral pecuniary externality, an increase in common ownership could stimulate the economy when the elasticity of labor supply is high relative to the elasticity of substitution in product markets. We characterize for which ownership structures the monopolistically competitive limit or an oligopolistic one is attained as the number of sectors in the economy increases. When firms have heterogeneous constant returns to scale technologies, we find that an increase in common ownership leads to markets that are more concentrated
Costly interpretation of asset prices
We propose a model in which investors cannot costlessly process information from asset prices. At the trading stage, investors are boundedly rational, and their interpretation of prices injects noise into the price, generating a source of endogenous noise trading. Our setup predicts price momentum and yields excessive return volatility and excessive trading volume. In an overall equilibrium, investors optimally choose sophistication levels by balancing the benefit of beating the market against the cost of acquiring sophistication. There can exist strategic complementarity in sophistication acquisition, leading to multiple equilibria
Mapping species richness of endemic macroinvertebrates by overlapping distribution maps
Els resultats de la
cartografia biogeogrà fica que es recolcen en predictors de significat ecològic derivats
dâinventaris faunĂstics (i.e. aquells que relacionen directament la riquesa dâespècies
amb variables explicatives) no acostumen a oferir resultats òptims a les escales
espacials dâordre mig i local, com les que aborda aquest treball en el marc de la Serra
de Tramuntana (Mallorca). A mode dâalternativa es proposa lâĂşs dâun mètode de
cartografia centrat en la diversitat dels tĂ xons. Aquesta aproximaciĂł modelitza la
probabilitat dâapariciĂł de dotze grups dâespècies endèmiques tot emprant les
variables ambientals com a predictors. AixĂ les coses, es representa la probabilitat
dâocurrència a partir de 48 punts de mostreig dâuna xarxa de 532 cel¡les dâ1 km2. A
partir de dites probabilitats es superposen els 12 mapes dâinferència per tal dâestimar la riquesa dâespècies a cada una de les 532 unitats dâanĂ lisi. Addicionalment es
proposa un mètode per detectar les falses absències aixà com les presències fortuïtes.
Aquestes observacions dubtoses sĂłn excloses del model de nĂnxol ecològic. En
paral¡lel a la representaciĂł de la riquesa dâespècies, sâaborden els patrons dâagrupaciĂł
dâespècies. La composiciĂł dels grups experimenta variacions importants, tot i que la
riquesa dâespècies roman constant. Aquesta invariabilitat en el nombre dâespècies no
sembla estar relacionada amb lâescassa variabilitat ambiental, ja que tant el marc
biòtic com lâabiòtic sĂłn diversos, aixĂ com tampoc amb la manca de correlaciĂł entre
espècies i medi (que es dona tant pel que fa a la composiciĂł dâespècies, aixĂ com
tambĂŠ amb la resposta especĂfica dâalgunes espècies). LâĂ rea dâestudi ĂŠs diversa des
dâun punt de vista ambiental i el volum dâespècies de macroinvertebrats ĂŠs de
moderat a important. La composiciĂł dels grups dâespècies presenta una correlaciĂł
significant amb el medi (temperatura mĂnima). El nombre de grups dâespècies
endèmiques per a un 92% de les unitats dâanĂ lisi oscil¡la entre 3 i 5. AixĂ doncs, la
cartografia de la biodiversitat a partir de tĂ xons sâha confirmat com una alternativa
và lida als mètodes convencionals fonamentats en inventaris. De mÊs a mÊs, la
proposta per tal de detectar les falses absències/presències resulta en una cartografia
de distribuciĂł especĂfica de les espècies força mĂŠs acurats
Coleoptera from the Chafarinas Islands (N Africa, Western Wediterranean): checklist and biogeographical implications
Abstract not availabl
Mapping species richness of endemic macroinvertebrates by overlapping distribution maps
Inventory-based approaches (i.e., those that directly relate species richness to explanatory variables) do not work on the medium and local scale that was studied in this paper; even when ecologically-meaningful environmental predictors were used. The use of an alternative approach (Taxon-based diversity mapping) is proposed. This approach starts by modelling the probability of occurrence of twelve target endemic species using environmental variables as predictors. Next, it projects the probability of occurrence from 48 sampled sites to a grid of 532 1-km2 units. Finally, the approach estimates endemic species richness at these 532 1-km2 units by overlapping the twelve maps inferred. We also propose a new approach whose purpose is to detect possible false absences and unstable presences. These doubtful observations were excluded from ecological niche modelling. In addition to species richness, the patterns experienced by species composition were analysed. Species composition experienced strong changes (i.e., large turnover), while species richness remained constant. This stasis in species richness is neither related to low environmental variability (both the biotic and abiotic scenarios are diverse) nor to the lack of species-environment relationships (not only species composition but also species-specific responses are correlated with environment). The area studied is environmentally diverse and species turnover of the macroinvertebrate community was moderate to large. Species composition was significantly correlated with environment (minimum temperature). The predicted number of target endemic species per cell in 92% of the studied area fell between 3 and 5. Therefore Taxonbased diversity mapping has been confirmed as a valid alternative to conventional inventory-based diversity mapping. Additionally, the new procedure proposed here for dealing with noisy presence/absence data produces more accurate distributional maps of individual species.Els resultats de la cartografia biogeogrĂ fica que es recolcen en predictors de significat ecològic derivats dâinventaris faunĂstics (i.e. aquells que relacionen directament la riquesa dâespècies amb variables explicatives) no acostumen a oferir resultats òptims a les escales espacials dâordre mig i local, com les que aborda aquest treball en el marc de la Serra de Tramuntana (Mallorca). A mode dâalternativa es proposa lâĂşs dâun mètode de cartografia centrat en la diversitat dels tĂ xons. Aquesta aproximaciĂł modelitza la probabilitat dâapariciĂł de dotze grups dâespècies endèmiques tot emprant les variables ambientals com a predictors. AixĂ les coses, es representa la probabilitat dâocurrència a partir de 48 punts de mostreig dâuna xarxa de 532 cel¡les dâ1 km2. A partir de dites probabilitats es superposen els 12 mapes dâinferència per tal dâestimar la riquesa dâespècies a cada una de les 532 unitats dâanĂ lisi. Addicionalment es proposa un mètode per detectar les falses absències aixĂ com les presències fortuĂŻtes. Aquestes observacions dubtoses sĂłn excloses del model de nĂnxol ecològic. En paral¡lel a la representaciĂł de la riquesa dâespècies, sâaborden els patrons dâagrupaciĂł dâespècies. La composiciĂł dels grups experimenta variacions importants, tot i que la riquesa dâespècies roman constant. Aquesta invariabilitat en el nombre dâespècies no sembla estar relacionada amb lâescassa variabilitat ambiental, ja que tant el marc biòtic com lâabiòtic sĂłn diversos, aixĂ com tampoc amb la manca de correlaciĂł entre espècies i medi (que es dona tant pel que fa a la composiciĂł dâespècies, aixĂ com tambĂŠ amb la resposta especĂfica dâalgunes espècies). LâĂ rea dâestudi ĂŠs diversa des dâun punt de vista ambiental i el volum dâespècies de macroinvertebrats ĂŠs de moderat a important. La composiciĂł dels grups dâespècies presenta una correlaciĂł significant amb el medi (temperatura mĂnima). El nombre de grups dâespècies endèmiques per a un 92% de les unitats dâanĂ lisi oscil¡la entre 3 i 5. AixĂ doncs, la cartografia de la biodiversitat a partir de tĂ xons sâha confirmat com una alternativa vĂ lida als mètodes convencionals fonamentats en inventaris. De mĂŠs a mĂŠs, la proposta per tal de detectar les falses absències/presències resulta en una cartografia de distribuciĂł especĂfica de les espècies força mĂŠs acurats
Flavour Issues in Leptogenesis
We study the impact of flavour in thermal leptogenesis, including the quantum
oscillations of the asymmetries in lepton flavour space. In the Boltzmann
equations we find different numerical factors and additional terms which can
affect the results significantly. The upper bound on the CP asymmetry in a
specific flavour is weaker than the bound on the sum. This suggests that --
when flavour dynamics is included -- there is no model-independent limit on the
light neutrino mass scale,and that the lower bound on the reheat temperature is
relaxed by a factor ~ (3 - 10).Comment: 19 pages, corrected equations for flavour oscillation