Concentration Indexes

Bu çalışmanın amacı havayolu pazarlarında piyasa yapısının analiz edilmesidir. Çalışmada gelişmekte olan ve gelişmiş ekonomilerde 2011-2020 dönemi için havayolu endüstrisinde pazar yapıları incelenmiştir. Ek olarak, Covid-19 salgınının havayolu piyasa yapısında meydana getirdiği bozulma da çalışmada incelenen unsurlar arasındadır. Çalışmada CR4, CR8 ve Herfindahl-Hirschman endeksi olmak üzere farklı analiz teknikleri kullanılmıştır. Çalışmanın bulgularına göre Covid-19’un yayılımının havayolu işletmelerini oldukça etkilediği ve bazı ülkelerde piyasa yapılarının değişmeye başladığı ortaya çıkarılmıştır. Ayrıca, rekabet düzeyi ve piyasa yapısılarının ülkeler arasında farklılık gösterdiği görülmüştür. Covid-19 nedeniyle ortaya çıkan bu durum, bazı ülkelerde daha yoğun pazarları öne çıkarırken bazı ülkelerde daha rekabetçi piyasaları gündeme getirmektedir.

Seaport has been widely evolved together with the increase of international trade and maritime transport. Most of nations with leading economic growth are recognized operating the largest port system such as Rotterdam port (Netherlands), Singapore port (Singapore) or Shanghai port (China). The seaport was conceptualized as a geographical area for mooring vessels to land for cargo loading and discharge, commonly a sheltered deep-water area (Stopford, 1997 [1]); however, being emerged as a major node in a supply chain network, integrating with hinterland through a system of transportation and other nodes

The purpose of the study is to analyse the market structure in airline markets. The research examined at market structures in the aviation sector for the years 2011 to 2020 in both developing and developed economies.. We analysed market concentration and market structure of many countries for the period 2011-2020. Additionally, we examined the deterioration caused by the Covid-19 pandemic in the airline market structure. In the study, we used different analyses such as CR4, CR8 and Herfindahl-Hirschman index. The study's conclusions show that the spread of Covid-19 has had a significant impact on airline firms, and market structures have started to shift in several nations.. The level of competition and the market structure differed among countries. Due to the Covid-19, while some countries experienced more intense markets, other countries experienced markets that are more competitive.

L'intérêt des méthodes récursives est de prendre en compte l'arrivée temporelle des informations et d'affiner ainsi au fil du temps les estimations. L'idée est d'utiliser les estimations calculées sur la base de données initiales et de les remettre à jour en tenant uniquement compte des nouvelles données arrivant dans la base. Le gain en terme de temps de calcul peut être très intéressant et les applications d'une telle approche sont nombreuses. Dans cet article, nous nous intéressons à la méthode SIR (sliced inverse regression, que l'on peut traduire par régression inverse par tranches) qui permet d'estimer le paramètre θ dans un modèle semi-paramétrique de régression du type y = f (x θ , ε) sans avoir à estimer le paramètre fonctionnel f ni à spécifier la loi de l'erreur ε. Dans le cas particulier où l'on considère H = 2 tranches, il est possible d'obtenir une expression analytique de l'estimateur de la direction de θ. Nous proposons dans cet article une forme récursive pour cet estimateur. Nous donnons des propriétés asymptotiques de cet estimateur (convergence presque sûre et normalité asymptotique). Nous illustrons aussi sur des simulations le bon comportement numérique de l'approche récursive proposée. Un avantage majeur de l'utilisation de la forme récursive est que les temps de calculs des estimateurs sont beaucoup plus courts que ceux obtenus avec la forme non récursive, en particulier lorsque la dimension de x est grande.

The purpose of the study is to analyse the market structure in airline markets. The research examined at market structures in the aviation sector for the years 2011 to 2020 in both developing and developed economies.. We analysed market concentration and market structure of many countries for the period 2011-2020. Additionally, we examined the deterioration caused by the Covid-19 pandemic in the airline market structure. In the study, we used different analyses such as CR4, CR8 and Herfindahl-Hirschman index. The study's conclusions show that the spread of Covid-19 has had a significant impact on airline firms, and market structures have started to shift in several nations.. The level of competition and the market structure differed among countries. Due to the Covid-19, while some countries experienced more intense markets, other countries experienced markets that are more competitive.

This research investigates the traffic share evolution of the container throughput in the Mediterranean ports from 2000 to 2015 considering hierarchical clustering and concentration indexes. Compositional Data analysis techniques are used to illustrate periods with similar traffic share composition. Two different regions (East and West) in the Mediterranean Sea (Med) are selected in the function of the long haul services. The standard concentration indexes (i.e., concentration ratio, Gini coefficient, and Normalized Herfindahl-Hirschman) reveal a gentle decreasing of the concentration with relevant fluctuations mainly in the East region. This is due to the investment in port infrastructure in the area resulting from privatization initiatives in many Eastern Mediterranean countries. The periods obtained from the hierarchical clustering show a differentiated pattern in traffic share composition. For these periods, the shift-share results are consistent with traffic fluctuations and in...

Background: Limited information still exists about the distribution of mental health (MH) in small districts. Considering the diversity in cultural specifications of entities in different societies, the current study aimed-assess the inequality of poor MH and corresponding socio-demographic components in a general population.
Methods: This population-based cross-sectional study was conducted in Gonabad City, North Eastern Iran. Data were collected by a general health questionnaire-28 (GHQ-28) assess MH status, considering a cut-off point of 23. The concentration index defines the inequality in the MH. Decomposition analysis was done-identify the contribution of each explanatory variable-the socioeconomic inequality in MH prevalence.
Results: Eight hundred subjects were recruited (response rate=98%); approximately 41.6% were aged 30 years or younger, half of whom were females. The overall prevalence of poor MH was 24.7% (95% CI: 21.8-27.9%) and the age-adjusted prevalence of poor MH was 27.5% (95% CI: 24.2-31.2%). A concentration of poor MH prevalence was observed among the poorest people (concentration index: -0.15). Socioeconomic Status (SES) (59.7%), age (24.1%), and gender (4.7%) were identified as the main contributors-socioeconomic-related inequality in poor MH prevalence.
Conclusion: Poor MH is significantly concentrated among the poorest people. Therefore, SES appeared-play a key role in improving the health of individuals, which can lead-improved health status in a community. Furthermore, these data suggest that the MH initiative should target the elderly and women via a recently determined family physician plan in Iran.

Urban Cooperative Banks are one of the key pillars of Indian economy. Over a long period of time, these banks have been catering to the financial needs of the people of urban and semi urban areas. Till 31 st March, 2021, RBI has included 54 major Urban Cooperative Banks in the 2nd schedule of the Reserve Bank of India Act, 1934 and those banks are being recognised as Scheduled Urban Cooperative Banks (SUCBs). The researchers used CRm and the Herfindahl-Hirschman Index (HHI) to measure the level of market concentration and competitiveness of SUCBs in this study to give the policy maker an idea of the concentration of the market and the competitiveness of the sector. It has been seen that despite the growing trend in HHI over the years, competition in the SUCB sector has not diminished significantly.

The introduction of hub-and-spoke operations in international container transportation and improved logistics systems has led to the concentration of port traffic and the potential emergence of super-hub container ports. On the other hand, the ambition to become such a super-hub has greatly stimulated the expansion of the container port sector and has created fierce inter-port competition; a trend that has actually led to the deconcentration of container transportation. Using alternative approaches for measuring concentration in the container port industry, this paper examines this trend empirically. The results reveal that for the last decade low concentration has dominated the container port industry in the Hamburg-Le Havre range and in the U. S. east and west coasts, while the market structure of container ports in Southern China has evolved from being highly concentrated to one that is very much deconcentrated.

This document describes two pedagogical tools developed for teaching applied microeconomics, specifically the issues related to concentration, dominance, stability and asymmetry of firms. The tools make a compilation of several concentration and stability indexes used in the literature since 1945. Among the benefits of the applications are the ease and agility to perform comparative analyzes of intersectorial and/or intertemporal type in a simple and agile way; and the use of unconventional concentration and stability measures.

For a large class of distributions and large samples, it is shown that estimates of the variance σ 2 and of the standard deviation σ are more often Pitman closer to their target than the corresponding shrinkage estimates which improve the mean squared error. Our results indicate that Pitman closeness criterion, despite its controversial nature, should be regarded as a useful and complementary tool for the evaluation of estimates of σ 2 and of σ. Résumé : Nous montrons dans cet article que certains estimateurs de la variance σ 2 et de l'écart type σ sont plus souvent proches de leur cible au sens de Pitman que les estimateurs correspondants obtenus par "shrinkage", pourtant connus pour améliorer l'erreur quadratique moyenne. Nos résultats sont valables asymptotiquement et pour une grande famille de lois de probabilité. Ils indiquent en particulier que le critère de proximité de Pitman, malgré sa nature controversée, devrait être envisagé comme un outil utile à l'évaluation de la qualité des estimateurs de σ 2 et de σ .

Gérard Biau1 and Yannis G. Yatracos2 Abstract: For a large class of distributions and large samples, it is shown that estimates of the variance σ2 and of the standard deviation σ are more often Pitman closer to their target than the corresponding shrinkage estimates which improve the mean squared error. Our results indicate that Pitman closeness criterion, despite its controversial nature, should be regarded as a useful and complementary tool for the evaluation of estimates of σ2 and of σ .

La directive europeenne MiFID du 1er novembre 2007, mise en application en France par l'AMF, a trouve recemment (et en particulier depuis la crise financiere) de nouveaux elements de justification. Sa mise en place souleve neanmoins des questions methodologiques (encore largement sous-estimees) relatives a l'analyse du comportement des investisseurs. Nous nous interessons ici aux implications de cette directive et proposons un cadre d'analyse pour l'etude des preferences des investisseurs, et pour l'evaluation de leurs implications au niveau de la gestion de portefeuille. En particulier, nous analysons les consequences d'une mauvaise adequation portefeuille-client investisseur. Pour ce faire, nous etudions les implications des biais de perception et de prediction des lois de probabilite des rendements financiers, a la fois dans le cadre de l'utilite esperee et dans celui de l'utilite non-esperee. Enfin, nous proposons une modelisation econometrique op...

Dans cette communication, nous nous interessons a la methode SIR (Sliced Inverse Regression, que l'on peut traduire par regression inverse par tranches) qui permet d'estimer le parametre $\theta$ dans un modele semi-parametrique de regression du type $y=f(x'\theta,\varepsilon)$ sans avoir a estimer le parametre fonctionnel $f$ ni a specifier la loi de l'erreur $\varepsilon$. Nous proposons un estimateur recursif de la direction de $\theta$ dans le cas particulier ou l'on considere $H=2$ tranches. Nous donnons des proprietes asymptotiques de cet estimateur (convergence et normalite asymptotique). Nous illustrons aussi sur des simulations le bon comportement numerique de la methode proposee.

This research investigates the traffic share evolution of the container throughput in the Mediterranean ports from 2000 to 2015 considering hierarchical clustering and concentration indexes. Compositional Data analysis techniques are used to illustrate periods with similar traffic share composition. Two different regions (East and West) in the Mediterranean Sea (Med) are selected in the function of the long haul services. The standard concentration indexes (i.e., concentration ratio, Gini coefficient, and Normalized Herfindahl-Hirschman) reveal a gentle decreasing of the concentration with relevant fluctuations mainly in the East region. This is due to the investment in port infrastructure in the area resulting from privatization initiatives in many Eastern Mediterranean countries. The periods obtained from the hierarchical clustering show a differentiated pattern in traffic share composition. For these periods, the shift-share results are consistent with traffic fluctuations and in...

The pressure of competition along with the incentive to extent control over ever larger and more complex logistic chains have strongly encouraged players to expand their services and scale of operations through vertical and horizontal integration, alliances and synergies. Evolutions in liner shipping as well as in terminal operations have led to a process of reorganization in both respective markets, increasing the concentration of market players. To this end, the aim of this paper is to investigate whether these concentration and centralization phenomena observed in the above markets extend also over the port phase, with selected ports concentrating large shares of container volumes. By employing several concentration methodologies, namely the CR4 and CR8, the HHI, the Gini Coefficient and the Lorenz concentration curves, as well as a Shift Share analysis, we investigate the evolution of concentration levels in U.S West and East Coast port ranges for the period between 2005 and 2015. As our results indicate, contrary to prior studies conducted, the U.S port ranges have evolved from deconcentrated towards, highly and moderately concentrated respectively. As such, results are relevant for policy makers and port experts, as they provide an up to date picture of the U.S port ranges.

Ces opinions doivent être considérées comme propres à leurs auteurs. 4 5 à mon petit frère Nicolas… 6 7 Remerciements J'adresse mes premiers remerciements à mon directeur de thèse, M. le Professeur Patrick ROGER. Je vous suis profondément reconnaissante pour votre rigueur, votre sens pédagogique, votre grande disponibilité et vos compétences dont j'ai pu bénéficier tout au long de ce travail. Vous avez trouvé la juste façon de m'encadrer, qui m'a permis d'évaluer et, surtout, de découvrir le monde passionnant de la recherche. Vous m'avez appris l'importance de la rigueur et fourni les outils nécessaires pour l'explorer. Je vous remercie aussi d'avoir été patient et de ne m'avoir laissé le choix durant les moments difficiles que j'ai vécu lors de ces années. Je suis consciente que ce n'était pas une thèse facile à diriger. Je remercie MM les Professeurs Jean-François Gajewski, Franck Moraux, Maxime Merli et Jacques Thépot de m'avoir fait l'honneur de composer mon jury. La soutenance de thèse est un moment que j'attends avec beaucoup d'impatience. Il s'agit pour moi d'un débat important et très enrichissant du fait que vous avez consacré votre temps et vos compétences à mon travail. Je vous en suis très reconnaissante. Je remercie toute l'équipe du LARGE d'avoir créé l'ambiance et les conditions de travail exceptionnelles dont j'ai pu bénéficier. En particulier, je tiens à remercier M le Professeur Maxime Merli de m'avoir dirigé vers Patrick ROGER tout au début de cette aventure; M le Professeur Laurent Weil pour son incroyable énergie positive et nos discussions qui m'ont permis d'avoir une meilleure visibilité de mon futur incertain; Mme la Professeur Marie-Hélène Broihanne qui avez toujours une idée me permettant d'avancer dans mon travail; Christophe Godlewski, pour sa réactivité et son aide très précieuse dans la rédaction d'un de mes chapitres.