In this paper, we assess the role of policies aimed at regulating the number and age structure of elections on the size and age structure of five European Academies of Sciences. We show the recent pace of ageing and the degree of variation in policies across them and discuss the implications of different policies on the size and age structure of academies. We also illustrate the potential effect of different election regimes (regimens? types?) (fixed vs. linked) and age structures of elections (younger vs. older) by contrasting the steady-state dynamics of different projections of Full Members in each academy into 2070 and measuring the size and age-compositional effect of changing a given policy relative to a status quo policy scenario. Our findings suggest that academies with linked intake (i.e., where the size of the academy below a certain age is fixed and the number of elections is set to the number of members becoming that age) may be a more efficient approach to curb growth without suffering any aging trade-offs relative to the faster growth of academies electing a fixed number of members per year. We further discuss the implications of our results in the context of stable populations open to migration.

Biodiversity, ecosystems, industry and human health are threatened by invasive plant species. The costs of mitigating damages run into billions of pounds per annum. Fundamental to the control of invasive plant species is an ability to predict which species will become invasive. Yet identification of predictive differences between invasive and non-invasive species has proven difficult to pinpoint. In this thesis I identify several weaknesses within published literature, and using field experiments and meta-analyses we address these to find consistent predictors of invasiveness amongst plants. Specifically, I recognize that predictors of invasiveness can be identified by studying plant species in the native range because species may undergo phenotypic and demographic changes following naturalization (Chapters 2 – 5). I also recognize the importance of comparing globally invasive and non-invasive species, and the importance of accounting for phylogenetic relationships so as not to inflate or conceal differences (Chapters 2 – 4). Finally, I investigate whether particular analyses are more appropriate for investigating life history and demographic differences (Chapter 5). This thesis comprises an introductory chapter (Chapter 1), four data chapters (Chapters 2 - 5) and a general discussion (Chapter 6). Chapters 2 and 3 compare life history traits of plant species known to be invasive elsewhere, with their exported but non-invasive sympatric relatives in the native range. Chapter 4 utilizes Population Projection Matrices held within the COMPADRE Plant Matrix Database, to compare demographic projections of stable and transient dynamics of invasive and non-invasive plants; and Chapter 5 compares ten metrics, derived from Population Projection Matrices, of seven invasive species between the native and invaded range to determine if there are demographic or life history differences that facilitate invasion, and to identify those analyses that are most likely to reveal such differences. I find reproductive capacity to be a predictor of invasiveness, and that analyses of transient dynamics are more likely than analyses of projected stable dynamics to reveal demographic or life history differences between invasive and non-invasive species or populations of plants. I discuss these findings in the context of invasive risk assessment protocols and highlight future research opportunities.

Submitted by Diego Gomes (diego.gomes@gmail.com) on 2016-04-26T18:23:39Z No. of bitstreams: 1 Thesis_Diego Braz Pereira Gomes.pdf: 1441990 bytes, checksum: eaa77253b29a0fe0108cafc8657d9327 (MD5) / Approved for entry into archive by Maria Almeida (maria.socorro@fgv.br) on 2016-05-09T12:55:02Z (GMT) No. of bitstreams: 1 Thesis_Diego Braz Pereira Gomes.pdf: 1441990 bytes, checksum: eaa77253b29a0fe0108cafc8657d9327 (MD5) / Approved for entry into archive by Maria Almeida (maria.socorro@fgv.br) on 2016-05-09T12:55:18Z (GMT) No. of bitstreams: 1 Thesis_Diego Braz Pereira Gomes.pdf: 1441990 bytes, checksum: eaa77253b29a0fe0108cafc8657d9327 (MD5) / Made available in DSpace on 2016-05-09T12:56:21Z (GMT). No. of bitstreams: 1 Thesis_Diego Braz Pereira Gomes.pdf: 1441990 bytes, checksum: eaa77253b29a0fe0108cafc8657d9327 (MD5) Previous issue date: 2013-01-13 / This thesis contains three chapters. The first chapter uses a general equilibrium framework to simulate and compare the long run effects of the Patient Protection and Affordable Care Act (PPACA) and of health care costs reduction policies on macroeconomic variables, government budget, and welfare of individuals. We found that all policies were able to reduce uninsured population, with the PPACA being more effective than cost reductions. The PPACA increased public deficit mainly due to the Medicaid expansion, forcing tax hikes. On the other hand, cost reductions alleviated the fiscal burden of public insurance, reducing public deficit and taxes. Regarding welfare effects, the PPACA as a whole and cost reductions are welfare improving. High welfare gains would be achieved if the U.S. medical costs followed the same trend of OECD countries. Besides, feasible cost reductions are more welfare improving than most of the PPACA components, proving to be a good alternative. The second chapter documents that life cycle general equilibrium models with heterogeneous agents have a very hard time reproducing the American wealth distribution. A common assumption made in this literature is that all young adults enter the economy with no initial assets. In this chapter, we relax this assumption – not supported by the data – and evaluate the ability of an otherwise standard life cycle model to account for the U.S. wealth inequality. The new feature of the model is that agents enter the economy with assets drawn from an initial distribution of assets. We found that heterogeneity with respect to initial wealth is key for this class of models to replicate the data. According to our results, American inequality can be explained almost entirely by the fact that some individuals are lucky enough to be born into wealth, while others are born with few or no assets. The third chapter documents that a common assumption adopted in life cycle general equilibrium models is that the population is stable at steady state, that is, its relative age distribution becomes constant over time. An open question is whether the demographic assumptions commonly adopted in these models in fact imply that the population becomes stable. In this chapter we prove the existence of a stable population in a demographic environment where both the age-specific mortality rates and the population growth rate are constant over time, the setup commonly adopted in life cycle general equilibrium models. Hence, the stability of the population do not need to be taken as assumption in these models. / Esta tese contém três capítulos. O primeiro capítulo usa um modelo de equilíbrio geral para simular e comparar os efeitos de longo prazo do Patient Protection and Affordable Care Act (PPACA) e de reduções de custos de saúde sobre variáveis macroeconômicas, orçamento do governo e bem-estar dos indivíduos. Nós encontramos que todas as políticas foram capazes de reduzir a população sem seguro, com o PPACA sendo mais eficaz do que reduções de custos. O PPACA aumentou o déficit público, principalmente devido à expansão do Medicaid, forçando aumento de impostos. Por outro lado, as reduções de custos aliviaram os encargos fiscais com seguro público, reduzindo o déficit público e impostos. Com relação aos efeitos de bem-estar, o PPACA como um todo e as reduções de custos melhoram o bem-estar dos indivíduos. Elevados ganhos de bem-estar seriam alcançados se os custos médicos norte-americanos seguissem a mesma tendência dos países da OCDE. Além disso, reduções de custos melhoram mais o bem-estar do que a maioria dos componentes do PPACA, provando ser uma boa alternativa. O segundo capítulo documenta que modelos de equilíbrio geral com ciclo de vida e agentes heterogêneos possuem muita dificuldade em reproduzir a distribuição de riqueza Americana. Uma hipótese comum feita nesta literatura é que todos os jovens adultos entram na economia sem ativos iniciais. Neste capítulo, nós relaxamos essa hipótese – não suportada pelos dados – e avaliamos a capacidade de um modelo de ciclo de vida padrão em explicar a desigualdade de riqueza dos EUA. A nova característica do modelo é que os agentes entram na economia com ativos sorteados de uma distribuição inicial de ativos. Nós encontramos que a heterogeneidade em relação à riqueza inicial é chave para esta classe de modelos replicar os dados. De acordo com nossos resultados, a desigualdade Americana pode ser explicada quase que inteiramente pelo fato de que alguns indivíduos têm sorte de nascer com riqueza, enquanto outros nascem com pouco ou nenhum ativo. O terceiro capítulo documenta que uma hipótese comum adotada em modelos de equilíbrio geral com ciclo de vida é de que a população é estável no estado estacionário, ou seja, sua distribuição relativa de idades se torna constante ao longo do tempo. Uma questão em aberto é se as hipóteses demográficas comumente adotadas nesses modelos de fato implicam que a população se torna estável. Neste capítulo nós provamos a existência de uma população estável em um ambiente demográfico onde tanto as taxas de mortalidade por idade e a taxa de crescimento da população são constantes ao longo do tempo, a configuração comumente adotada em modelos de equilíbrio geral com ciclo de vida. Portanto, a estabilidade da população não precisa ser tomada como hipótese nestes modelos.