7 research outputs found
Optimal surplus reinsurance
Mestrado Bolonha em Actuarial ScienceNeste trabalho, procura-se optimizar o resseguro de surplus, que é um tipo de resseguro proporcional em que as proporções variam com o capital seguro, com base numa linha de retenção e num limite à apólice de resseguro. A optimização é efectuada numa carteira baseada em apólices reais de seguro de incêndio.
Realiza-se esta optimização com recurso a três diferentes critérios de optimalidade, baseados na utilidade esperada, no desvio-padrão e no Value-at-Risk da riqueza da seguradora. Quando nos foi possível, obtivemos expressões que podem ser resolvidas para encontrar o contrato de resseguro óptimo. Contudo, a dificuldade de as resolver analiticamente leva-nos a optimizá-las numericamente. Sempre que não conseguimos obter tais expressões, recorremos a simulações para encontrar o contrato de resseguro óptimo. Tais optimizações são efectuadas sob diferentes comissões de resseguro e diferentes princípios de prémio para as apólices primárias.
Os nossos resultados sugerem pelo menos quatro conclusões possíveis. Em primeiro lugar, nenhum dos três critérios de optimalidade empregues é claramente melhor do que os outros, embora o da utilidade esperada tenha tendência para produzir resultados mais avessos ao risco. Em segundo lugar, o uso do desvio-padrão como princípio do prémio para as apólices primárias costuma apresentar resultados melhores — com maiores valores esperados por comparação com os desvios-padrão, bem como Values-at-Risk mais favoráveis — do que os princípios do valor esperado e da variância. Em terceiro lugar, os nossos resultados salientam a importância de que a comissão de resseguro cubra razoavelmente as despesas da seguradora, a fim de gerar resultados admissíveis. Finalmente e talvez mais interessante, concluímos que o contrato de resseguro de surplus óptimo terá, pelo menos bastante frequentemente, um limite à apólice de resseguro suficientemente baixo para que não cubra totalmente os riscos mais elevados.In this work, we seek to optimise surplus reinsurance, which is a type of proportional reinsurance where proportions vary with the sum insured, based on a retention line and on a reinsurance policy limit. Optimisation is done on a portfolio which is based on reallife fire insurance policies.
We perform this optimisation by resorting to three different optimality criteria, which are based on the expected utility, the standard deviation and the Value-at-Risk of the insurer’s wealth. Where we found it to be possible, expressions were derived which can be solved to find the optimal reinsurance contract. However, the difficulty in solving them analytically leads us to optimise them numerically. Where we could not derive such expressions, we resorted to simulations in order to find the optimal reinsurance contract. Such optimisations are carried out under different reinsurance commissions and different premium principles for the primary policies.
Our findings suggest at least four possible conclusions. Firstly, none of the three optimality criteria used is clearly better than the other ones, although the expected utility criterion tends to yield more risk-averse results. Secondly, usage of the standard deviation as the primary premium principle generally provides better results — with higher expected values by comparison to the standard deviations, as well as more favourable Values-at-Risk — than the expected value and the variance principles. Thirdly, our results highlight the importance that the reinsurance commission provide a reasonable cover for the expenses of the insurer, in order to produce acceptable outcomes. Lastly and perhaps more interestingly, we conclude that the optimal surplus reinsurance contract will, at least quite frequently, feature a reinsurance policy limit low enough to not fully cover the highest risks.info:eu-repo/semantics/publishedVersio
NEOTROPICAL CARNIVORES: a data set on carnivore distribution in the Neotropics
Mammalian carnivores are considered a key group in maintaining ecological health and can indicate potential ecological integrity in landscapes where they occur. Carnivores also hold high conservation value and their habitat requirements can guide management and conservation plans. The order Carnivora has 84 species from 8 families in the Neotropical region: Canidae; Felidae; Mephitidae; Mustelidae; Otariidae; Phocidae; Procyonidae; and Ursidae. Herein, we include published and unpublished data on native terrestrial Neotropical carnivores (Canidae; Felidae; Mephitidae; Mustelidae; Procyonidae; and Ursidae). NEOTROPICAL CARNIVORES is a publicly available data set that includes 99,605 data entries from 35,511 unique georeferenced coordinates. Detection/non-detection and quantitative data were obtained from 1818 to 2018 by researchers, governmental agencies, non-governmental organizations, and private consultants. Data were collected using several methods including camera trapping, museum collections, roadkill, line transect, and opportunistic records. Literature (peer-reviewed and grey literature) from Portuguese, Spanish and English were incorporated in this compilation. Most of the data set consists of detection data entries (n = 79,343; 79.7%) but also includes non-detection data (n = 20,262; 20.3%). Of those, 43.3% also include count data (n = 43,151). The information available in NEOTROPICAL CARNIVORES will contribute to macroecological, ecological, and conservation questions in multiple spatio-temporal perspectives. As carnivores play key roles in trophic interactions, a better understanding of their distribution and habitat requirements are essential to establish conservation management plans and safeguard the future ecological health of Neotropical ecosystems. Our data paper, combined with other large-scale data sets, has great potential to clarify species distribution and related ecological processes within the Neotropics. There are no copyright restrictions and no restriction for using data from this data paper, as long as the data paper is cited as the source of the information used. We also request that users inform us of how they intend to use the data
Brazilian Flora 2020: Leveraging the power of a collaborative scientific network
International audienceThe shortage of reliable primary taxonomic data limits the description of biological taxa and the understanding of biodiversity patterns and processes, complicating biogeographical, ecological, and evolutionary studies. This deficit creates a significant taxonomic impediment to biodiversity research and conservation planning. The taxonomic impediment and the biodiversity crisis are widely recognized, highlighting the urgent need for reliable taxonomic data. Over the past decade, numerous countries worldwide have devoted considerable effort to Target 1 of the Global Strategy for Plant Conservation (GSPC), which called for the preparation of a working list of all known plant species by 2010 and an online world Flora by 2020. Brazil is a megadiverse country, home to more of the world's known plant species than any other country. Despite that, Flora Brasiliensis, concluded in 1906, was the last comprehensive treatment of the Brazilian flora. The lack of accurate estimates of the number of species of algae, fungi, and plants occurring in Brazil contributes to the prevailing taxonomic impediment and delays progress towards the GSPC targets. Over the past 12 years, a legion of taxonomists motivated to meet Target 1 of the GSPC, worked together to gather and integrate knowledge on the algal, plant, and fungal diversity of Brazil. Overall, a team of about 980 taxonomists joined efforts in a highly collaborative project that used cybertaxonomy to prepare an updated Flora of Brazil, showing the power of scientific collaboration to reach ambitious goals. This paper presents an overview of the Brazilian Flora 2020 and provides taxonomic and spatial updates on the algae, fungi, and plants found in one of the world's most biodiverse countries. We further identify collection gaps and summarize future goals that extend beyond 2020. Our results show that Brazil is home to 46,975 native species of algae, fungi, and plants, of which 19,669 are endemic to the country. The data compiled to date suggests that the Atlantic Rainforest might be the most diverse Brazilian domain for all plant groups except gymnosperms, which are most diverse in the Amazon. However, scientific knowledge of Brazilian diversity is still unequally distributed, with the Atlantic Rainforest and the Cerrado being the most intensively sampled and studied biomes in the country. In times of “scientific reductionism”, with botanical and mycological sciences suffering pervasive depreciation in recent decades, the first online Flora of Brazil 2020 significantly enhanced the quality and quantity of taxonomic data available for algae, fungi, and plants from Brazil. This project also made all the information freely available online, providing a firm foundation for future research and for the management, conservation, and sustainable use of the Brazilian funga and flora
NEOTROPICAL ALIEN MAMMALS: a data set of occurrence and abundance of alien mammals in the Neotropics
Biological invasion is one of the main threats to native biodiversity. For a species to become invasive, it must be voluntarily or involuntarily introduced by humans into a nonnative habitat. Mammals were among first taxa to be introduced worldwide for game, meat, and labor, yet the number of species introduced in the Neotropics remains unknown. In this data set, we make available occurrence and abundance data on mammal species that (1) transposed a geographical barrier and (2) were voluntarily or involuntarily introduced by humans into the Neotropics. Our data set is composed of 73,738 historical and current georeferenced records on alien mammal species of which around 96% correspond to occurrence data on 77 species belonging to eight orders and 26 families. Data cover 26 continental countries in the Neotropics, ranging from Mexico and its frontier regions (southern Florida and coastal-central Florida in the southeast United States) to Argentina, Paraguay, Chile, and Uruguay, and the 13 countries of Caribbean islands. Our data set also includes neotropical species (e.g., Callithrix sp., Myocastor coypus, Nasua nasua) considered alien in particular areas of Neotropics. The most numerous species in terms of records are from Bos sp. (n = 37,782), Sus scrofa (n = 6,730), and Canis familiaris (n = 10,084); 17 species were represented by only one record (e.g., Syncerus caffer, Cervus timorensis, Cervus unicolor, Canis latrans). Primates have the highest number of species in the data set (n = 20 species), partly because of uncertainties regarding taxonomic identification of the genera Callithrix, which includes the species Callithrix aurita, Callithrix flaviceps, Callithrix geoffroyi, Callithrix jacchus, Callithrix kuhlii, Callithrix penicillata, and their hybrids. This unique data set will be a valuable source of information on invasion risk assessments, biodiversity redistribution and conservation-related research. There are no copyright restrictions. Please cite this data paper when using the data in publications. We also request that researchers and teachers inform us on how they are using the data
Growing knowledge: an overview of Seed Plant diversity in Brazil
Abstract An updated inventory of Brazilian seed plants is presented and offers important insights into the country's biodiversity. This work started in 2010, with the publication of the Plants and Fungi Catalogue, and has been updated since by more than 430 specialists working online. Brazil is home to 32,086 native Angiosperms and 23 native Gymnosperms, showing an increase of 3% in its species richness in relation to 2010. The Amazon Rainforest is the richest Brazilian biome for Gymnosperms, while the Atlantic Rainforest is the richest one for Angiosperms. There was a considerable increment in the number of species and endemism rates for biomes, except for the Amazon that showed a decrease of 2.5% of recorded endemics. However, well over half of Brazillian seed plant species (57.4%) is endemic to this territory. The proportion of life-forms varies among different biomes: trees are more expressive in the Amazon and Atlantic Rainforest biomes while herbs predominate in the Pampa, and lianas are more expressive in the Amazon, Atlantic Rainforest, and Pantanal. This compilation serves not only to quantify Brazilian biodiversity, but also to highlight areas where there information is lacking and to provide a framework for the challenge faced in conserving Brazil's unique and diverse flora