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  • Frände, Joakim (Suomalainen lakimiesyhdistys, 2013)
    Dual residence in the taxation of individuals Each country has the right to determine on which grounds and to what extent it exercises its tax authority. In the case of individuals a country usually bases its right to levy taxes on the connection between the country and the individual, or the country and the income or wealth in question. This thesis deals with the connection that exists between the country and the individual. Under domestic tax law systems a separation is usually made into full and limited tax liability. Full tax liability arises when there are strong ties between the individual and the state. Residence is usually considered a strong tie that results in full tax liability. A person who is resident in a country, and therefore subject to full tax liability, is usually taxed on his world wide income. However, if the person is not resident, the state does not claim the right to tax the individual as such, but taxes income that arises within the territory of the country. When determining residence in one country, no consideration is given to whether the person is also resident in other countries. Consequently, individuals can as a result of cross border movement be considered resident both in the country of arrival and the country of departure. When two countries both consider an individual resident, dual residence arises. The purpose of this thesis is to analyse three aspects of dual residence. First and foremost, national rules on residence will be analysed, as well as how dual residence occurs in practice. Secondly, the rules on how to determine tax residence for tax treaty purposes are discussed. Thirdly, the tax consequences of dual residence will be investigated. The emphasis will be on the first two aspects of dual residence mentioned. The thesis is based on a dogmatic approach to legal research. Some elements of comparative methods of research are also present. A person who is resident in Finland is subject to full tax liability in Finland. Residence for income tax purposes is determined in the income tax act (ITA) § 11. According to ITA § 11 a person is resident in Finland if he has his main abode and home in Finland, stays over six months in Finland or falls under the three-year rule. Finnish nationals who leave Finland are as a result of the three-year rule considered resident the year of departure and the three following years. Limited tax liability can arise before the three- year period ends if the individual can produce evidence that he lacks substantial ties to Finland. The Finnish rules on residence are partly problematic. The rules on when a visit to Finland has fulfilled the six months requirement are unclear. Also, the three-year rule does not specify what a substantial tie is. The three-year rule furthermore distinguishes between Finnish nationals and foreign nationals. Different tax consequences depending on nationality can be problematic from an EU perspective. A short analysis of the current ECJ cases, however, indicates that the three-year rule is probably in conformity with EU law. Residence is also used to determine tax liability for the purpose of other taxes, such as the gift and inheritance tax, car tax, municipal tax and social security contributions. Each above-mentioned tax has its own notion of residence. The different concepts of residence are compared with the residence concept that is used for income tax purposes. The comparison led to the observation that the residence concept for income tax purposes can impact on the other residence concepts. Usually residence for other tax purposes does not impact on the residence status for income tax purposes. However, the tax authorities claim that belonging to the Finnish social security system is a substantial tie according to the three-year rule. The Finnish rules on residence for income tax purposes are in many ways interesting in comparison to other countries rules on residence. A comparison has been made with Sweden, Norway, Denmark, Germany, the United Kingdom and the USA. Most of the above-mentioned countries have fairly recently amended and modernized their rules on residence. The comparison demonstrates that the Finnish rules on residence are outdated and in need of reformation. For instance, nationality does not carry any weight when determining tax liability in most other countries (except for the USA). When a Finnish national moves abroad, he is usually subject to full tax liability in the country of arrival, and at the same time subject to full tax liability in Finland due to the three-year rule. The resulting dual residence is solved by tax treaty, provided that the countries have concluded a treaty. For tax treaty purposes a person can only have one tax treaty residence at a time. Residence for tax treaty purposes is determined through the tie breaker in article 4(2). The state of residence has the primary right to tax the individual. The tie breaker is, however, problematic, since the criteria on which residence is decided are partly ambiguous and can be interpreted in different ways. Therefore the general rules on tax treaty interpretation have to be considered. Rules on tax treaty interpretation can be found in domestic legislation, international law, the Vienna convention, article 3(2) of tax treaties, and in the commentaries to the model tax convention. Some of the rules on interpretation can lead to different outcomes. The parties can also have diverging information about the individual s personal circumstances. Therefore it is possible that two countries cannot reach an agreement on which country should be the individual s state of residence according to article 4. When both countries claim to be the state of residence, the conflict shall be settled by the mutual agreement procedure in article 25 of the tax treaty. The mutual agreement procedure is time consuming and results cannot be guaranteed. In Finland there are no publications by the tax authorities on the mutual agreement procedure, and the procedure is hence not very well known. Therefore, I have tried to describe how the mutual agreement procedure is executed in practice. In 2008 the OECD added an arbitration clause to its model convention as a final means to solve tax treaty disputes that have not been solved by the mutual agreement procedure. Finland has not, however, included the clause in its treaties. Dual residence can result in several different consequences for the taxation of individuals, and the possible consequences are analysed in this thesis. The taxation of dual resident individuals can vary greatly from one situation to another depending on domestic legislation in both countries of residence, the type of income, the source of income, the tax treaties articles and the interpretation of the tax treaty. The taxation of dual resident persons can be divided into situations where no tax treaty has been concluded, a tax treaty exists and Finland is not the state of residence, and situations where both countries claim residence status according to the tax treaty. Some Finnish tax treaties include the three-year rule in article 23. According to the clause the source country is granted a more comprehensive, but secondary, right to tax persons who are resident according to domestic tax law, although the residence state for tax treaty purposes is in the other country. To demonstrate the impact of dual residence on the taxation of individuals, the taxation in Finland of interest, dividend, capital gains, salary and pensions is described through practical examples. Situations of dual residence can also have other tax implications, e.g. is there a progressive impact on other income, and how are deductions and losses taken into account when Finland is not the state of residence according to article 4? Dual residence does not necessarily cause double taxation as a result of national rules on credit and exemption and the elimination of double taxation. The concluding chapter sheds light on some of the most urgent problems in the current legislation on residence and presents some suggestions for improvements. The rules on residence in the domestic income tax act are scrutinized in detail. It is suggested that the nationality criterion in the three-year rule is abolished, and that substantial ties are defined in the income tax act. Furthermore, it is also suggested that the national rules on the elimination of double taxation are elucidated and that the scale of application is extended. On the international level it is recommended that article 3(2) in the OECD model tax convention is amended to primarily recommend an interpretation according to the context. Some minor adjustments are also presented to the articles on residence and mutual agreement.
  • Holopainen, Sari (Helsingin yliopisto, 2015)
    The boreal biome harbours a large share of the world s wetlands, and is the main breeding area for several duck species. Breeding habitats strongly influence duck reproduction. In this study, the habitat use of ducks and their breeding success was estimated in a boreal landscape in southern Finland. A review of duck habitat use in boreal wetlands was additionally made. Boreal forest lakes are normally considered stable environments, but from a duck s point of view both resource abundance and habitat quality in the lakes may differ from one year to another. In this study the vegetation of boreal freshwater lakes was found to slowly change during the 20-year study period. Beavers (Castor canadensis) caused pronounced alterations in the lakes by flooding them. Flooding rendered lake vegetation structure more luxuriant and increased the lake use by ducks. In general, duck brood lake use was positively associated with both the coverage of wide belts of tall emergent plants and the abundance of emerging insects and aquatic invertebrates. The relative importance of these factors varied between species. The brood production of common goldeneyes (Bucephala clangula) was regulated by density dependence per se, but fluctuated with food availability per capita. No spatial density-dependent effects were found for the common teal (Anas crecca), but the breeding success was instead explained well by habitat quality variation. Both food and flood abundance had a positive effect, but different variables seemed to operate during different phases of the breeding season. Many aspects of boreal breeding ducks are still poorly studied. Especially lacking are studies concerning duckling survival and the effects of anthropogenic actions on duck habitat use. This research underlines the importance of high quality habitats for breeding duck populations in the boreal landscape. The varying habitat requirements of duck species should be considered when implementing wetland management.
  • Monaco,Danilo (2000)
    Even though trade wars between Italy and France were definitely not a new phenomenon, when in 1969 the six members of the EEC decided to lay down the foundations of the wine common market, they hardly imagined the consequences that this kind of decision would have implied later on. For the first time ever French leadership was seriously threatened by import wines: by the spring 1975, when the first symptoms of overproduction appeared, the stage was set for the harshest trade conflict ever occured between two of the major partners of the common market area. Accusations of despicable economic practices hampering the principle of free trade were facing claims of illegal dumping exercises. Starting from a simple model on reciprocal dumping developed by Brander and Krugman (1983), this paper analyses the impact on dumping practices among economies with imperfectly competitive industries and firms producing homogeneous output. Particular emphasis is given to the problem of market leadership and of modelling trade as a multi-stage game where retaliation plays a fundamental role. The impact of different strategic tools as tariffs and subsidies is analysed, together with the overall effect of trade or autarky on overall welfare. While the theory often suggest equivocal payoffs, when considering the case of France-Italy wine trade and in the light of available evidence, the long run gains brought about to French consumers in the form of lower prices, reduced monopoly power and increased competition seem to have outweighed the losses incurred by its producers. Even though rationale for trade inhibiting practices has been in this paper theoretically shown to be sound, we have seen that retaliation often wipes off the benefits coming about through tariffs, subsidies and the likes. Ultimately, all the argumentation introduced in this paper braces more or less directly the free trade solution, since trade increases welfare through the effect of a reduced degree of monopoly in each country. This is a solution desirable under the pure economic point of view.
  • Rantala, Kati (2001)
    Studien analyserar modernistisk bildkonstfostran, som riktar sig till ungdomar. Denna fostran är upplysande, universaliserande och avskild från övrig samhällelig eller konstteoretisk diskussion. Enligt pedagogiken ökar konstaktiviteter förmågan att uttrycka sig fritt och individuellt. Detta medför att eleverna utvecklar sin personlighet, mognar andligt och lär sig leva ett etisk acceptabelt liv. Studien redogör för hur bildkonstfostran möter och försöker påverka den unge eleven och hans individualitet. Därutöver dryftar studien de utmaningar dagens samhälle ställer på bildkonstfostran: det ökade medvetandet om svårigheten att definiera konst och det allmänna goda, den ständiga betoningen av individens rätt att välja samt ungdomarnas egna visuella och estetiska kulturer. Materialet består av intervjuer med bildkonstelever och deras lärare, basläroplanen i konst samt intervjumaterial om nutidskonst och andra fritidsaktiviteter. I analysen tolkas betydelser och talesätt som ingår i materialet. Bildkonstfostran är en institution som eftersträvar det allmänna goda. Samtidigt försöker den legitimera sin verksamhet. Utan begreppet konst klarar sig institutionen inte. Detta ger upphov till retoriska problem och återvändsgränder: idén om konstens positiva verkan förpliktar konstpedagogerna att förse eleverna med färdigheter, som bottnar i sättet att uppfatta konst. För att skilja konsten från övrig symbolisk och produktiv verksamhet uppfattas den, i enlighet med traditionell estetik, som ett bildformspråk och som ett sätt att gestalta världen. Å andra sidan anses konsten vara ett sätt att fritt uttrycka känslor eller rentav kulminationen av mänsklig utveckling. I en mångkulturell debatt definieras konsten ofta som något som alltid existerat i alla kulturer. Men vad är i så fall inte konst? När "konst" förknippas med individens självuttryck har vi att göra med en några sekel lång social konstruktion. Eleverna tillägnar sig lätt lärarnas individualiserande talesätt. Uttrycket "du måste själv komma fram till det" beskriver lärarna lika väl som eleverna; som mål är det individuella uttrycket en paradox. Å andra sidan är det en självklarhet; eleverna framställer unika bilder och ger dem egna betydelser. När eleverna bedömer sina konkreta arbeten vill de veta hur deras färdigheter utvecklas. De vill utvärdera sin skicklighet, varvid tillfredsställelsen med sig själva grundar sig på att de flexibelt lär sig de regler och färdigheter som deras aktiviteter bygger på.
  • Torppa, Kaisa (2014)
    The purpose of this thesis was to examine the diversity and species composition of dung beetle (Scarabaeinae) communities in degraded rainforest landscapes in southeastern Madagascar. Several studies elsewhere in the world have revealed that forest-dwelling dung beetle communities and especially large species suffer from forest degradation and fragmentation by decreased species diversity. The most important factors affecting community structure of forest-dwelling dung beetles are habitat area, connectivity and vegetation quality i.e. microclimate. The hypothesis of this study was that the situation is the same in Madagascar. As dung beetles provide several important ecosystem services, like nutrient cycling and bioturbation, loss of dung beetle diversity imposes a secondary threat to the extraordinary nature of Madagascar by decreasing the regeneration ability of vegetation. Material for the study was collected in forest fragments of different size and quality between two areas of primary tropical rainforest – Ranomafana National Park and Vatovavy mountain – in November and December 2011 and January 2012. The sampling was conducted by transects of 30–60 fish- or carrion-baited pitfall traps which were set up in 55 localities in the study area. In each locality, several variables were measured to describe the vegetation and microclimatic conditions. The variables included temperature, humidity, estimate of vegetation quality by 6 observation-based classes, vegetation density, hights of three clearly visible vegetation layers, altitude and slope steepness. In addition, connectivities were measured for the localities using GIS and a satellite image –based vegetation classification. In order to demonstrate the differences between certain localities the study sites were divided into seven zones in terms of their distance from the Ranomafana National Park, average connectivity of the transects and elevation. Altogether 4,199 individuals belonging to 24 species were collected. Six of the species are currently under identification process in the Paris Museum of Natural History. According to the preliminary results they include two species new to science. Largest numbers of species were collected from good quality fragments between Ranomafana and Vatovavy. Also, a clear transition zone in species composition was detected a few kilometers west from Vatovavy, where altitude changes sharply. The study reveals that the species assemblages in the forest fragments and degraded forest areas are surprisingly species rich. This may, however, be partly because of extinction debt, and many of the still surviving species may soon die out due to restricted dispersal possibilities. Connectivity and vegetation quality were shown to have an effect on Canthonini species richness, with less species in less connected areas and lower vegetation quality. Vegetation quality was also shown to have an impact on the proportions of species with different body length: more small and medium-sized (< 8 mm) species were found in fragments where vegetation was more degraded. In addition to revealing how rainforest fragmentation and degradation affect local communities, the study gives interesting information about the distribution of certain species of Epilissus (Scarabaeinae: Canthonini). It has been known before that four species of Epilissus show elevational differentiation in their occurrence in Ranomafana. In this study, two more species of the same genus, E. prasinus and E. emmae obscurpennis, were shown to continue this pattern in lower elevations near Vatovavy mountain, about 50 kilometers east of Ranomafana.
  • Viljanen, Heidi (Helsingin yliopisto, 2009)
    The traditional aim of community ecology has been to understand the origin and maintenance of species richness in local communities. Why certain species occur in one place but not in another, how ecologically apparently similar species use resources, what is the role of the regional species pool in affecting species composition in local communities, and so forth. Madagascar offers great opportunities to conduct such studies, since it is a very large island that has been isolated for tens of million of years. Madagascar has remarkable faunal and floral diversity and species level endemism reaches 100% in many groups of species. Madagascar is also exceptional for endemism at high taxonomic levels and for the skewed representation of many taxa in comparison with continental faunas. For example, native ungulates that are dominant large herbivorous mammals on the African continent are completely lacking in Madagascar. The largest native Malagasy herbivores, and the main dung producers for Malagasy dung beetles, are the endemic primates, lemurs. Cattle was introduced to Madagascar about 1,000 yrs ago and is today abundant and widespread. I have studied Malagasy dung beetle communities and the distributional patterns of species at several spatial scales and compared the results with comparable communities in other tropical areas. There are substantial differences in dung beetle communities in Madagascar and elsewhere in the tropics in terms of the life histories of the species, species ecological traits, local and regional species diversities, and the sizes of species geographical ranges. These differences are attributed to Madagascar s ancient isolation, large size, heterogeneous environment, skewed representation of the mammalian fauna, and recent though currently great human impact.
  • Wirta, Helena (Helsingin yliopisto, 2009)
    Speciation on islands is affected by island size and the range of habitats and resources available and often also by limited interactions with other taxa. An ancestral population may evolve into a large number of species via an adaptive radiation. In Madagascar, most groups of animals and plants have radiated on the island, having arrived via oceanic dispersal during the long isolation of Madagascar. Characteristic features of Malagasy biota are exceptionally high level of endemism, high species richness as well as lack of many higher taxa that are dominant on the African mainland. Malagasy dung beetles are dominated by two tribes, Canthonini and Helictopleurina, with more than 250 endemic species. In this thesis I have reconstructed molecular phylogenies for the two tribes using several gene regions and different phylogenetic methods. Evolution of closely related species and among populations of the same species was examined with haplotype networks. The Malagasy Canthonini consists of three large lineages, while Helictopleurina forms a monophyletic group. The ancestors of each of the four clades colonised Madagascar at different times during Cenozoic. The subsequent radiations differ in terms of the number of extant species (from 37 to more than 100) and the level of ecological differentiation. In addition, Onthophagini (6 species) and Scarabaeini (3) have colonised Madagascar several times, but they have not radiated and the few species have not entered forests where Canthonini and Helictopleurina mostly occur. Among the three Canthonini radiations, speciation appears to have been mostly allopatric in the oldest and the youngest clades, while in the Epactoides clade sister species have diverged in their ecologies but have similar geographical distributions, indicating that speciation may have occurred in regional sympatry. The most likely isolating mechanisms have been rivers and forest refugia during dry and cool geological periods. Most species are generalists feeding on both carrion and dung, and competition among ecologically similar species may prevent their coexistence in the same communities. Some species have evolved to forage in the canopy and a few species have shifted to use cattle dung, a new resource in the open habitats following the introduction of cattle 1500 years ago. The latter shift has allowed species to expand their geographical ranges.
  • Hyvärinen, Heini (2010)
    Johdanto: Ikääntyessä iholla tapahtuva D-vitamiininmuodostus heikkenee ja lihakset ja luusto haurastuvat. Heikko lihaskunto on yhteydessä kaatumisriskiin, ja kaatuminen on yleisin syy vanhusten murtumiin. Monissa tutkimuksissa on osoitettu, että luustovaikutustensa lisäksi D-vitamiinilla on vaikutuksia luurankolihakseen. D-vitamiinihoidon on osoitettu vähentävän kaatumisia, mikä saattaa osin selittyä parantuneen tasapainon kautta. Joissakin tutkimuksissa on havaittu heikko tilastollinen yhteys Dvitamiinin ja kroonisen kivun välillä. D-vitamiinin puutokseen liitettyjä kipuja on esitetty luustoperäisiksi, mutta D-vitamiinin lihasvaikutukset huomioiden ne saattavat olla ainakin osin lihasperäisiä. Tavoitteet: Tämän poikkileikkaustutkimuksen tavoitteena oli tutkia, onko seerumin 25-hydroksi-Dvitamiinipitoisuus (25OHD) yhteydessä lihastoimintoihin itsenäisesti kotona asuvilla reumatauteja sairastavilla yli 50-vuotiailla. Hypoteesina oli, että D-vitamiinin puutos on yhteydessä heikentyneisiin neuromuskulaarisiin lihastoimintoihin, joita tässä tutkimuksessa mitattiin tasapainon perusteella. Aineisto ja menetelmät: Tutkimukseen rekrytoitiin yli 50-vuotiaita, koska tässä kohderyhmässä lihastoimintojen heikentymisen ja D-vitamiinin puutoksen odotettiin olevan yleisiä. Tutkittavien tuli kuitenkin olla kohtalaisen hyväkuntoisia, jotta he jaksaisivat fyysiset testit ja tutkimuksen mahdollisesti aiheuttaman henkisen rasituksen. Siksi lihastoimintojen ongelmia kuvaamaan valittiin polymyalgia rheumaticaa sairastavia, itsenäisesti kotona asuvia ihmisiä. Tutkimukseen osallistui myös joitakin yli 50- vuotiaita fibromyalgiaa ja nivelreumaa sairastavia henkilöitä. Seerumin 25OHD-pitoisuus määritettiin EIA-menetelmällä (IDS, UK). D-vitamiinin yhteyttä tutkittiin tasapainoon (Rombergin vakio tasapainolevyllä) ja lihasvoimaan (puristusvoima molempien käsien parhaan tuloksen keskiarvona, jalkojen nopeusvoima hyppylevyllä), kipuun ja toimintakykyyn. Tilastomenetelminä käytettiin ristiintaulukointia, t-testiä, lineaarista regressiota, logistista regressiota ja Pearsonin korrelaatiota. Tulokset: Tutkimukseen osallistui 47 henkilöä, joista viisi oli miehiä. Potilaat olivat 53-81 -vuotiaita (keski-ikä 70 v) ja hieman ylipainoisia (BMI 28). 25OHD oli keskimäärin 64 nmol/l. Ravitsemustila oli keskimäärin hyvä (MNA-pisteet 24). 25OHD oli alle 50 nmol/l 32 %:lla ja vastaavasti alle 75 nmol/l 74 %:lla tutkittavista. Potilaista 83 % käytti D-vitamiinivalmistetta. 25OHD korreloi positiivisesti ravitsemustilan (MNA) ja käänteisesti tasapainon ja kiputiheyden kanssa. 25OHD, ikä, sukupuoli ja MNA-pisteet selittivät 13,9 % (adjusted r2) huojunnan vaihtelusta ja 14,5 % (r2 Cox & Snell) kiputiheyden vaihtelusta. Ainoastaan 25OHD-pitoisuudella oli tilastollisesti merkitsevä itsenäinen selitysosuus huojuntaan (p = 0,024) ja kiputiheyteen (p = 0,045). Niillä, joilla 25OHD oli vähintään 75 nmol/l, oli 83 % pienempi riski kärsiä päivittäisestä kivusta kuin niillä, joilla 25OHD-pitoisuus oli alle 75 nmol/l. Lihasvoimalla, lihasmassalla ja kivun voimakkuudella ei havaittu yhteyttä D-vitamiinistatukseen. Johtopäätökset: Tässä tutkimuksessa reumatauteja sairastavien yli 50-vuotiaiden potilaiden matalat 25OHD-pitoisuudet olivat yhteydessä tasapainovaikeuksiin ja päivittäisiin kipuihin. Lihasmassa ja lihasvoima eivät olleet yhteydessä D-vitamiinistatukseen. Löydösten pohjalta olisi tulevaisuudessa tarpeen tutkia tarkemmin D-vitamiinikorvaushoidon vaikutuksia tasapainomittareihin ja kiputiheyteen.
  • Kairema, Anna (Helsingin yliopisto, 2013)
    This dissertation brings contribution to two interrelated topics. The first contribution concerns the so-called systems of dyadic cubes in the context of metric spaces. Second contribution is applications to one and two weight norm inequalities for linear and sublinear positive integral operators. Both of the topics are important in harmonic analysis and an ongoing area of study. The main novelties of the presented works consist of improving and extending existing results into more general frameworks. The work consists of four research articles and an introductory part. The first two articles, written in collaboration with T. Hytönen, study systems of dyadic cubes in metric spaces. In the Euclidean space, dyadic cubes are well-known and define a convenient structure with useful covering and intersection properties. Such dyadic structures are central especially in the modern trend of harmonic analysis. In the first article extensions of these structures are constructed in general geometrically doubling metric spaces. These consist of a refinement of existing constructions and a completely new construction of finitely many adjacent dyadic systems which behave like "translates" of a fixed system but without requiring a group structure. In this context, "cubes" are not properly cubes but rather more complicated sets that collectively have properties reminiscent of those in the Euclidean case. However, it is natural to ask what type of sets could or should be regarded cubes. In the second paper, we give a complete answer to this question in the general framework of a geometrically doubling metric space making use of the "plumpness" notion already appeared in the geometric measure theory. From another side; the two latter articles study weighted norm inequalities. Via the new construction of adjacent dyadic systems, weighted estimates for positive integral operators are obtained in a general framework. In the third paper, the two-weight problem is investigated for potential-type operators. Both strong and weak type estimates are characterized by "testing type" conditions: to show the full norm inequality it suffices to test the desired estimate on a specific class of simple test functions only. The results improve some previous results in the sense that the considered ambient space is more general (with more general measures and no additional geometric assumptions) and the testing is over a countable collection of test function only (instead of a significantly larger collection appearing in the previous works on the topic). The main technical novelty of the proof is a decomposition of the operator, along dyadic systems giving rise to certain finitely many "dyadic" versions of the original operator. In the fourth article, the focus is on sharp constant estimates for generalized fractional integral operators. A positive answer and its sharpness are given in the context of a space of homogeneous type. The result is reduced to weak-type inequalities using the results in the third paper. The sharpness requires a construction of functions that locally behave similarly to the basic power functions on the Euclidean space. The result extends a recent Euclidean result. Keywords: dyadic cube, adjacent dyadic systems, metric space, space of homogeneous type, potential type operator, testing condition, weighted norm inequality, sharp bound
  • Luther, Fred (1945)
  • Nyberg, Henri (2006)
    Ekonometrisessa tutkimuksessa dynaamisia binäärisiä aikasarjamalleja on toistaiseksi tutkittu kohtuullisen vähän. Viime vuosina on kuitenkin esitetty useita uusia aikasarjamalleja. Tässä tutkielmassa pääpaino on Kaupin ja Saikkosen (2005) esittämissä probit-malleissa, joissa tarkasteltavan aikasarjan viivästettyjä havaintoja sisältävää ns. dynaamista probit-mallia laajennetaan uudella ns. autoregressiivisella osalla. Tutkielman teoriaosassa tarkastellaan probit-mallien ominaisuuksia, kuten parametrien suurimman uskottavuuden estimointia sekä mallien diagnostiikkaan ja ennustamiseen liittyviä kysymyksiä. Parametrien estimoinnin yhteydessä havainnollistetaan uuden autoregressiivisen osan tuomia muutoksia perinteisiin ns. staattisiin probit-malleihin nähden. Hypoteesien testaamista käsittelevässä kappaleessa esitetään kaksi autoregressiivisen osan tarpeellisuutta testaavaa LM-testiä. Teoreettisia tarkasteluita sovelletaan tutkielman empiriaosassa suhdannesyklien ennakointiin, jossa tavoitteena on ennustaa esiintyneitä taloudellisia taantumajaksoja. Aineistona käytetään Yhdysvaltojen ja Saksan vuodesta 1972 alkavaa kuukausiaineistoa, joka on koottu useista eri lähteistä. Lähdekirjallisuudessa hyödyllisiksi ennakoiviksi taantumaindikaattoreiksi havaittujen tuottokäyrien, eli pitkän ja lyhyen koron erotusten, lisäksi käytetään myös muita selittäviä muuttujia, kuten tarkasteltavaan maahan nähden ulkomaista tuottokäyrää sekä maiden pörssien osaketuottoja. Aivan uutena selittäjänä tarkastellaan maiden välistä korkoeroa. Otoksen sisäisissä ja vuonna 2001 alkaneen viimeisimmän taantumajakson keinotekoisissa otoksen ulkopuolisissa ennusteissa Kaupin ja Saikkosen esittämät uudet ns. dynaaminen autoregressiivinen ja autoregressiivinen malli osoittautuvat käyttökelpoisimmiksi malleiksi. Monissa tutkimuksissa käytetty staattinen malli vaikuttaisi olevan käyttökelpoinen lähinnä pitkissä vuoden pituisissa ennusteissa. Vuoden 2001 taantumaa ennustettaessa parhaimmat mallit antoivat selkeät taantumasignaalit kolmesta kuuteen ehtäviä johtopäätöksiä. Maiden kotimaisen tuottokäyrän ohella myös osaketuotoilla ja ulkomaisella tuottokäyrällä havaitaan tilastollisesti merkitsevää ennustevoimaa. Yhdysvaltojen ja Saksan välinen korkoero näyttäisi olevan hyödyllinen selittäjä Saksan tapauksessa. Tutkielman tärkein lähde on Kaupin ja Saikkosen (2005) artikkeli. Teoriaosan kannalta keskeisiä lähteitä ovat Davidsonin ja MacKinnonin kirja (1993) sekä autoregressiivisen osan LM-testiä esitettäessä heidän artikkelinsa (1984) apumallit. Suhdannesyklisovelluksessa tutkielman kannalta keskeisimpiä ovat Bernardin ja Gerlachin (1998) sekä Estrellan ja Mishkinin (1998) artkuukautta ennen taantumajakson alkua. Ennustetehokkuuden kasvaessa mallien dynaamiset rakenteet muuttavat samalla selittävistä muuttujista tikkelit, joissa käsitellään samoja selittäviä muuttujia kuin tässä tutkimuksessa, mutta staattista probit-mallia käyttäen. Empiiristä osaa varten käytiin lävitse edellä mainittujen lähteiden lisäksi laajasti muita suhdannesyklien ennustamiseen ja korkojen tuottokäyriin liittyviä tutkimuksia.
  • Nyberg, Henri (2007)
    Binäärisiä aikasarjoja on toistaiseksi ekonometrisessa tutkimuksessa tutkittu kohtuullisen vähän. Viime vuosina on kuitenkin esitetty uusia aikasarjamalleja, joissa yksinkertaisinta ns. staattista mallia on laajennettu erilaisilla dynaamisilla rakenteilla. Tutkimuksessa tarkastellaan Yhdysvaltojen ja Saksan taantumajaksojen ennustamista Kaupin ja Saikkosen (2007) esittämiä uusia dynaamisia ns. autoregressiivisen rakenteen sisältäviä malleja käyttäen. Aiemmin käytettyihin malleihin tehtävän vertailun lisäksi usean kuukauden pituisten ennusteiden yhteydessä tutkitaan heidän esittämää uutta ns. iteratiivista ennustemenetelmää aiemmin käytettyyn suoraan menetelmään nähden. Tutkimuksen teoriaosassa tarkastellaan dynaamisten probit-mallien ominaisuuksia, kuten parametrien suurimman uskottavuuden estimointia sekä mallien diagnostiikkaan ja ennustamiseen liittyviä kysymyksiä. Hypoteesien testaamista käsittelevässä luvussa esitetään kaksi autoregressiivisen osan tarpeellisuutta testaavaa LM-testiä. Mallien estimoinneissa sekä estimointijakson ulkopuolelle muodostetuissa ennusteissa ns. autoregressiivisen osan sisältämät mallit osoittautuvat käyttökelpoisimmiksi malleiksi. Parhaimmat mallit antavat mm. selkeät taantumasignaalit ennen vuonna 2001 alkanutta, viimeksi esiintynyttä, taantumajaksoa. Dynaamisen probit-mallin tapauksessa iteratiiviset ennusteet ovat suoria ennusteita parempia. Lyhyen ja pitkän koron välinen erotus, eli tuottokäyrä, on aiempien tutkimusten havaintojen tapaan erityisen hyvä taantumajaksoja ennakoiva selittävä muuttuja. Maiden kotimaisten tuottokäyrien lisäksi myös ulkomaisella tuottokäyrällä sekä maiden osaketuotoilla havaitaan tilastollisesti merkitsevää ennustevoimaa. Yhdysvaltojen ja Saksan välinen korkoero näyttäisi olevan hyödyllinen selittäjä Saksan tapauksessa. Tutkimuksen tärkein lähde on Kaupin ja Saikkosen (2007) artikkeli. Mallien rakentelun ja ennustemenetelmien kannalta myös Chauvetin ja Potterin (2005) artikkeli on merkittävä. Teoriaosan kannalta keskeisiä lähteitä ovat Davidsonin ja MacKinnonin kirja (1993) sekä autoregressiivisen osan LM-testiä esitettäessä heidän artikkelinsa (1984) apumallit. Taantumajaksojen ennustamisessa keskeisimpiä ovat Bernardin ja Gerlachin (1998) sekä Estrellan ja Mishkinin (1998) artikkelit. Korkojen, erityisesti tuottokäyrän, ja osaketuottojen taantumaennustevoimaa on lisäksi tarkasteltu useissa muissakin tutkimuksissa.
  • Nyberg, Henri (2007)
    In the econometric literature, there is not much research on binary time series. However, in the last couple of years, some new binary time series models have been suggested where the traditional static model is extended by different kinds of dynamic structures. In the thesis, the main goal is to forecast the economic recession periods occurred in the United States and Germany. Especially, it is interesting to consider new so called autoregressive models suggested by Kauppi and Saikkonen (2007). They also proposed a new iterative framework for multiperiod forecasts. Iterated multiperiod forecasts are compared with previously used direct forecasts. The parameter estimation of the employed dynamic models can be done by a maximum likelihood method described in the theoretical part of the thesis. Model diagnostics and forecasting procedures are as well considered. Two LM tests for the usefulness of the autoregressive part are also proposed. It is shown that the models with autoregressive part seem to outperform the static probit models in terms of in-sample and out-of-sample predictions. The best forecasting models give the distinct recession signals of the forthcoming recession which started in 2001. In the dynamic probit model with the lagged recession indicator, the iterative forecasts seem to be superior to direct forecasts. Several empirical studies have proposed that the yield curve, which is defined as a spread between long and short term interest rates, is an accurate explanatory variable in recession forecasting. As in previous studies, the domestic yield curve is an important predictor variable in both countries but also the foreign yield curve, stock market returns and, in the case of Germany, the interest rate differential between the United States and Germany are statistically significant predictors in the dynamic probit models. The most important reference is the article of Kauppi and Saikkonen (2007). Chauvet and Potter (2005) have also proposed important model variants and forecasting methods for the binary time series models. Davidson and MacKinnon’s book (1993) and their article (1984) are important references for the theoretical part and especially for the proposed LM tests for the autoregressive part. The articles of Bernard and Gerlach (1998) and Estrella and Mishkin (1998) are important references for the recession forecasting. The forecasting power of the yield curves and the stock returns are also considered in numerous other articles.
  • Karpechko, Alexey (Helsingin yliopisto, 2007)
    Transport plays an important role in the distribution of long-lived gases such as ozone and water vapour in the atmosphere. Understanding of observed variability in these gases as well as prediction of the future changes depends therefore on our knowledge of the relevant atmospheric dynamics. This dissertation studies certain dynamical processes in the stratosphere and upper troposphere which influence the distribution of ozone and water vapour in the atmosphere. The planetary waves that originate in the troposphere drive the stratospheric circulation. They influence both the meridional transport of substances as well as parameters of the polar vortices. In turn, temperatures inside the polar vortices influence abundance of the Polar Stratospheric Clouds (PSC) and therefore the chemical ozone destruction. Wave forcing of the stratospheric circulation is not uniform during winter. The November-December averaged stratospheric eddy heat flux shows a significant anticorrelation with the January-February averaged eddy heat flux in the midlatitude stratosphere and troposphere. These intraseasonal variations are attributable to the internal stratospheric vacillations. In the period 1979-2002, the wave forcing exhibited a negative trend which was confined to the second half of winter only. In the period 1958-2002, area, strength and longevity of the Arctic polar vortices do not exhibit significant long-term changes while the area with temperatures lower than the threshold temperature for PSC formation shows statistically significant increase. However, the Arctic vortex parameters show significant decadal changes which are mirrored in the ozone variability. Monthly ozone tendencies in the Northern Hemisphere show significant correlations (|r|=0.7) with proxies of the stratospheric circulation. In the Antarctic, the springtime vortex in the lower stratosphere shows statistically significant trends in temperature, longevity and strength (but not in area) in the period 1979-2001. Analysis of the ozone and water vapour vertical distributions in the Arctic UTLS shows that layering below and above the tropopause is often associated with poleward Rossby wave-breaking. These observations together with calculations of cross-tropopause fluxes emphasize the importance of poleward Rossby wave breaking for the stratosphere-troposphere exchange in the Arctic.
  • Eloranta, Satu (Helsingin yliopisto, 2013)
    A knowledge base is considered a system that is told information about an external world and that answers questions about this world. Our goal here is to outline knowledge bases that involve both knowledge and beliefs. In previous studies, various kinds of belief change have been studied in isolation, but we want to tie them together. We aim at knowledge bases that could carry the epistemic states of agents, that is, the knowledge and the beliefs that an agent has at any one moment in time. The difference between knowledge and belief is that while knowledge increases monotonically with time, beliefs may at some later point in time turn out to be false. Beliefs may change for various reasons: in belief revision, beliefs are changed when receiving new information about a world that has not changed, while in belief update a change in the world is to be recorded. Different types of change call for different treatments. In belief-change studies, various change types have been characterized by rationality criteria set on each type. The main principles in these criteria are maintaining consistency of beliefs and minimality of change. When dealing with belief change, our approach is to take knowledge as an integrity constraint that should always hold, and we describe how the rationality criteria should be modified accordingly. In our refined rationality criteria, beliefs that are inconsistent with the knowledge of the knowledge base will never be allowed to enter into the knowledge base. In the rationality criteria, a common assumption is that the most recent information is the most reliable, and it has therefore been prioritized over the old beliefs. However, this may not be the case in all circumstances. In order to complete the collection of belief-change types, we propose a new, commutative type of change for entering competing evidence into the knowledge base. The representation theorems that have been given for belief revision indicate that belief revision involves an ordering of disbelief on possible alternative situations, or equivalently, an epistemic entrenchment on logical formulas. A formula less entrenched is more easily given up when eliminating inconsistancies. In view of the changes in the rationality criteria, we also refine the representation theorems. We introduce two finite representations for knowledge bases, one with a finite ordered set of propositional formulas that are satisfiable but pairwise inconsistent with each other, and the other with a finite list of pairwise inconsistent propositional formulas. Both representations involve dynamic orderings of disbelief that have arisen out of the previous change operations. We show that for the knowledge base to satisfy the rationality criteria given for belief revision, the dynamic ordering of disbelief in the knowledge base is vital. The representations and the operators that we introduce in this thesis demonstrate how this ordering of disbelief could be dealt with in various operations.
  • Fornaro, Paolo (2011)
    In recent years, thanks to developments in information technology, large-dimensional datasets have been increasingly available. Researchers now have access to thousands of economic series and the information contained in them can be used to create accurate forecasts and to test economic theories. To exploit this large amount of information, researchers and policymakers need an appropriate econometric model.Usual time series models, vector autoregression for example, cannot incorporate more than a few variables. There are two ways to solve this problem: use variable selection procedures or gather the information contained in the series to create an index model. This thesis focuses on one of the most widespread index model, the dynamic factor model (the theory behind this model, based on previous literature, is the core of the first part of this study), and its use in forecasting Finnish macroeconomic indicators (which is the focus of the second part of the thesis). In particular, I forecast economic activity indicators (e.g. GDP) and price indicators (e.g. consumer price index), from 3 large Finnish datasets. The first dataset contains a large series of aggregated data obtained from the Statistics Finland database. The second dataset is composed by economic indicators from Bank of Finland. The last dataset is formed by disaggregated data from Statistic Finland, which I call micro dataset. The forecasts are computed following a two steps procedure: in the first step I estimate a set of common factors from the original dataset. The second step consists in formulating forecasting equations including the factors extracted previously. The predictions are evaluated using relative mean squared forecast error, where the benchmark model is a univariate autoregressive model. The results are dataset-dependent. The forecasts based on factor models are very accurate for the first dataset (the Statistics Finland one), while they are considerably worse for the Bank of Finland dataset. The forecasts derived from the micro dataset are still good, but less accurate than the ones obtained in the first case. This work leads to multiple research developments. The results here obtained can be replicated for longer datasets. The non-aggregated data can be represented in an even more disaggregated form (firm level). Finally, the use of the micro data, one of the major contributions of this thesis, can be useful in the imputation of missing values and the creation of flash estimates of macroeconomic indicator (nowcasting).