One of the main tenets of finance is diversification. Investors choose their portfolios so as to diversify away their idiosyncratic risk. In four essays included into this dissertation the implications of less than perfect diversification on investors’ performance and asset pricing are investigated. In Essay I we examine one particular instance in which diversification may play a role in a non-portfolio type of investment: the IPO. In an IPO, a set of potentially non-diversified investors – the existing shareholders – reduce their holdings of a company, listing the company and selling part of its shares. Our contribution is to show how portfolio diversification of controlling investors in private companies affects the IPO process. We demonstrate that companies sold by more diversified shareholders are less likely to be taken public, but when doing so they are priced more favourably. In Essays II and III we investigate the impact of incomplete diversification and imperfect risk-sharing on asset returns. Our argument is that the smaller shareholder base a firm has, the larger the fraction of company idiosyncratic risk on average its investors have to carry, and the higher return they would demand for that. We demonstrate that there is a negative and significant relationship between companies’ shareholder base and stock returns as well as between changes in shareholder base and stock returns. This effect is more pronounced for younger companies, but remains significant for seasoned companies as well. Applying our analysis to corporate events we demonstrate that abnormal performance following the repurchase can be partially explained by the reduction in the shareholders base resulting from repurchase. In Essay IV I investigate the motives behind one of the most puzzling examples of investors’ underdiversification – the local bias. Contrary to the predictions of classical financial theories, investors on aggregate overweight stock of proximate companies in their portfolios. I demonstrate that being placed in new community, individual investors not only soon become biased towards companies with establishments in this new locality, but they also obtain superior returns from these investments. Investing into the local stocks, therefore, is to a large degree rational. / Diss. Stockholm : Handelshögskolan, 2005 S. ii-vi: sammanfattning, s. 1-134: 4 uppsatser

L’évaluation et la gestion des stocks de poissons ont pour objectif d’atteindre une exploitation durable des ressources fournies par les océans. Si les progrès dans ce domaine sont bien réels pour certains stocks de grande importance commerciale, la situation est différente pour les stocks dits à données limitées. Souvent historiquement moins exploités, ces stocks ne bénéficient pas des mêmes ressources, tant économiques qu’humaines, pour réaliser une évaluation de stock permettant par la suite la mise en place de mesures de gestion. Ce travail s’appuie sur deux cas d’étude, le lieu jaune (Pollachius pollachius) et la seiche (Sepia officinalis), afin d’explorer des méthodologies d’évaluation de stocks adaptées aux situations de données limitées. Après une première partie introductive reprenant le contexte de l’évaluation des stocks et présentant les deux cas d’étude, une revue des méthodes d’évaluation de stocks à données limitées est proposée. Une troisième partie compare les résultats d’un modèle de biomasse à deux stades et d’un modèle multi-annuel de déplétion généralisé appliqués au stock de seiche de Manche. Une version améliorée du modèle de biomasse à deux stades codé en Bayésien est également présentée. Le travail se poursuit avec l’application d’un modèle d’analyse intégrée Stock Synthesis au stock de lieu jaune de mer Celtique. Les résultats sont comparés aux résultats de modèles plus simples nécessitant moins de données. Les résultats du modèle Stock Synthesis s’avèrent sensibles aux hypothèses sur la valeur de mortalité naturelle, dont le calcul dépend des paramètres de croissance du stock. La cinquième partie présente l’acquisition et le traitement de nouvelles données qui pourront permettre une meilleure estimation de l’état du stock de lieu jaune. Un modèle hiérarchique Bayésien est construit, permettant un transfert d’information entre trois stocks et la mise à jour des paramètres biologiques du lieu jaune. Le dernier chapitre conclut ce travail en reprenant les principaux résultats obtenus et en élargissant la discussion sur des perspectives de recherche. / The assessment and the management of fish stocks aim at achieving a sustainable exploitation of the resources provided by the oceans. While progress have been made in this field for some stocks of great commercial importance, the situation is different for the so-called “data limited” stocks. Often historically less exploited, these stocks do not benefit from the same economical resources nor workforce to conduct the stock assessments required to set management measures. This work is based on two case studies, pollack (Pollachius pollachius) and cuttlefish (Sepia officinalis). The aim is to investigate the stock assessment methods adapted to data-limited situations. A first introductive part presents the background of fish stock assessment as well as the two case studies. This first chapter is followed by a review of data-limited stock assessment methods. The third part compare the results of a two-stage biomass model with the results of a multi-annual generalized depletion model applied to the English Channel stock of cuttlefish. An improved version of the Bayesian two-stage biomass model is also presented. In the fourth part, a Stock Synthesis model based on integrated analysis methods is applied to the stock of pollack in the Celtic Seas Ecoregion. The results are compared to the results of simpler models which require less data. The Stock Synthesis model results are sensitive to the assumptions on the natural mortality value, which relies on the growth parameters of the stock. The fifth part presents the collection and analysis of new data which will allow a better estimate of pollack stock status. A Bayesian hierarchical model is constructed, allowing information transfer between three stocks and the update of pollack biological parameters. The last chapter concludes this work by summarizing the main results. The discussion is extended to the research perspectives.

Many companies do not prioritize warehouse logistics sufficiently in their core business, with the help of increased knowledge, more companies can reduce non-value-creating activities on their warehouse space. There is research and methods designed for standard warehouses that help reduce picking time and non-value-adding activities, however, there is not enough research regarding companies with limited warehouse space and how they can work towards continuous improvement. The purpose and contribution of the study is increasing knowledge of how companies with limited warehouse space can manage and time-efficient their warehouse space with the help of warehouse logistics. A qualitative case study has been performed with observations and an interview where picking time has been the main focus. The collection of the theoretical framework has been reviewed and revised through scientific articles and other literature to strengthen the empirical research. The research is delimited and focuses on limited storage areas. More specifically, the study has placed its emphasis on warehouse logistics and picking time. The study looked at a company's limited storage space and focused on a small part in a delivery, from arrival control to storage. In the empirical study, a case company has been studied and confirmed that warehouse logistics needs to be given better priority in companies with limited warehouse space. With the help of reduced time in warehouse routines, many companies can reduce non-value-creating activities. The purpose of the study and issues will contribute to future research and can be used as a basis. Future research will also help other companies in the same situation to eliminate non-value-adding activities and reduce picking time. / Många företag prioriterar inte lagerlogistik tillräckligt i sin kärnverksamhet, med hjälp av en ökad lagerlogistik-kunskap kan fler företag reducera icke-värdeskapande aktiviteter på lagerytan. Det exister forskning och metoder som är utformade för standardlager som hjälper till att reducera plocktid och icke-värdeskapande aktiviteter, däremot saknas det tillräcklig forskning gällande företag med begränsad lageryta och hur dom kan arbeta mot ständiga förbättringar när det kommer till lagerlogistik.  Studiens syfte och bidrag ligger i att öka kunskapen om hur företag med begränsad lageryta, med hjälp av lagerlogistik, kan hantera och tidseffektivisera sin lageryta. En kvalitativ fallstudie har utförts med observationer och mejlkommunikation där plocktid varit huvudfokus. Samling av det teoretiska ramverket har genom vetenskapliga artiklar och annan litteratur granskats och reviderats för att stärka den empiriska undersökningen. Forskningen avgränsas och fokuserar på begränsade lagerytor. Mer specifikt har studien lagt sin vikt på lagerlogistik och plocktid. Studien har tittat på ett fallföretags begränsade lageryta och på en liten del i en leverans, från ankomstkontroll till förvaringsförråd.  I den empiriska undersökningen har ett fallföretag studerats och bekräftat att lagerlogistik behöver prioriteras bättre hos företag med begränsad lageryta. Med hjälp av reducerad tid vid lagerrutiner kan många företag reducera icke-värdeskapande aktiviteter. Studiens syfte och frågeställningar kommer att bidra till framtida forskningar och kan användas som underlag. Framtida forskning kommer även bidra med att hjälpa andra företag i samma sits att eliminera icke-värdeskapande aktiviteter och reducera plocktid.