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- Citizens' freedom to choose representatives: ballot structure, proportionality and "fragmented" parliamentsPublication . Pereira, Paulo T.; Silva, João Andrade eThe analysis of the political consequences of electoral laws has emphasized how individual characteristics of the electoral system (electoral formulas, district magnitude, ballot structure) affect the degree of parliament "fragmentation" and proportionality. This paper argues that the personal attributes of representatives are also an important consequence of electoral laws, and that they are in part determined by citizens' freedom to choose representatives. We clarify this concept and develop an index of citizens' freedom to choose members of parliament as a function of the ballot structure, district size and electoral formulae. Using data from twenty nine countries, we find that neither proportionality nor the effective number of parties is significantly affected by voters' freedom of choice. This result has important normative implications for electoral reform.
- Comparison of time series with unequal lengthPublication . Caiado, Jorge; Crato, Nuno; Peña, DanielThe comparison and classification of time series is an important issue in practical time series analysis. For these purposes, various methods have been proposed in the literature, but all have shortcomings, especially when the observed time series have different sample sizes. In this paper, we propose spectral domain methods for handling time series of unequal length. The methods make the spectral estimates comparable, by producing statistics at the same frequency. A first sensible approach may consist on zero-padding the shorter time series in order to increase the corresponding number of periodogram ordinates. We show that this works well provided the sample sizes are not very different, but does not give good results in case the time series lengths are very unbalanced. For this latter case, we study some periodogram-based comparison methods and construct a test. Both the methods and the test display reasonable properties for series of any lengths. Additionally and for reference, we develop a parametric comparison method. The procedures are assessed by a Monte Carlo simulation study. As an illustrative example, a periodogram method is used to compare and cluster industrial production series of some developed countries.
- Covariate measurement error : bias reduction under response-based samplingPublication . Ramalho, Esmeralda A.In this paper we propose a general framework to deal with the presence of covariate measurement error (CME) in response-based (RB) samples. Using Chesher’s (1991) methodology, we obtain a small error variance approximation for the contaminated sampling distributions that characterise RB samples with CME. Then, following Chesher (2000), we develop generalised method of moments (GMM) estimators that reduce the bias of the most well known likelihood-based estimators for RB samples which ignore the existence of CME and derive a score test to detect the presence of this type of measurement error. Our approach only requires the specification of the conditional distribution of the response variable given the latent covariates and the classical additive measurement error model assumption, the availability of information on both the marginal probability of the strata in the population and the variance of the measurement error not being essential. Monte Carlo evidence is presented which suggests that, in RB samples of moderate sizes, the bias-reduced GMM estimators perform well
- Econometric modelling of the short-term interest rate : an application to PortugalPublication . Cassola, Nuno; Nicolau, João; Sousa, JoãoIn this paper we estimate and compare, for Portugal, several econometric models of the short-term interest rate inspired in the continuous-time models of Vasicek, and Cox, Ingersoll and Ross. The models are first estimated using the Generalised Method of Moments. The empirical results motivate estimating the short-term interest rate process using a regime switching technique where regimes follow a Markov chain. Some applications to term structure modelling and contingent claim valuation are carried out.
- Effects of immigration on intra-industry trade: a logit analysisPublication . Faustino, Horácio C.; Proença, IsabelThis study estimates the effects of the immigration stock, as well as those of immigrants’ characteristics, such as having the same language as that of the host country and the level of qualification or entrepreneurship, on Portuguese intra-industry trade (IIT) by types, controlling for the effects of other socio-economic factors, like economic dimensions, price indexes and distance. In addition to the member-countries of the EU-27, the group of countries studied includes five African countries with Portuguese as their official language, known as the PALOPs, and the BRIC countries. Since indexes are fractional variables, the pseudo-likelihood Logit estimator was used on the panel data to obtain the empirical results. The study found that an increase of the immigrant stock will produce an increment in the trade indexes considered and this effect is enhanced if immigrants originate from a country where Portuguese is the official language, or if they are highly qualified, whereas immigrant entrepreneurs have no significant effect
- Ergodic properties of polygonal billiards with strongly contracting reflection lawsPublication . Magno, Gianluigi Del; Dias, João Lopes; Duarte, Pedro; Gaivão, José PedroWe consider convex polygonal billiards with a reflection law that contracts the reflection angle towards the normal. Polygonal billiards with orthogonal reflections are called slap maps. For polygons without parallel sides facing each other, the slap map has a finite number of ergodic absolutely continuous invariant probability measures. We show that any billiard with a strongly contracting reflection law has the same number of ergodic SRB measures with the same mixing periods as the ergodic absolutely continuous invariant probabilities of its corresponding slap map. The case of billiards in regular polygons and triangles is studied in detail.
- Estimativas 'Jackknif' e 'Bootstrap' para o enviesamento e desvio padrão do índice de GiniPublication . Proença, IsabelNeste trabalho serão apresentados os métodos "Jacknife" e "Bootstrap" Ilustrando-se as suas potencialidades com o exemplo númérico onde se aplicam estas técnicas ao indice de concentração de Gini.
- A GARCH-based method for clustering of financial time series: International stock markets evidencePublication . Caiado, Jorge; Crato, NunoIn this paper, we introduce a volatility-based method for clustering analysis of financial time series. Using the generalized autoregressive conditional heteroskedasticity (GARCH) models we estimate the distances between the stock return volatilities. The proposed method uses the volatility behavior of the time series and solves the problem of different lengths. As an illustrative example, we investigate the similarities among major international stock markets using daily return series with different sample sizes from 1966 to 2006. From cluster analysis, most European markets countries, United States and Canada appear close together, and most Asian/Pacific markets and the South/Middle American markets appear in a distinct cluster. After the terrorist attack on September 11, 2001, the European stock markets have become more homogenous, and North American markets, Japan and Australia seem to come closer.
- Grandparents and women's participation in the labor marketPublication . Albuquerque, Paula C.; Passos, JoséThe conciliation of work and family life is a challenge to most women. In some countries, although not in southern Europe, women make significant use of part-time schedules as a way of balancing work and family life. Informal care, typically care by grandparents, is an alternative. It is cheap, trustworthy, and possibly compatible with non-standard labor schedules. In this paper we investigate how childcare by grandparents affects the probability of working of mothers in southern European countries. We empirically evaluate the verification and the significance of such an effect, accounting for a potentially endogenous grandparent-caring status.
- How do work and public policies interact with child poverty?Publication . Arcanjo, Maria Manuela; Bastos, Amélia; Nunes, Francisco; Passos, JoséChild poverty is a problem firmly recognized in the industrialized world. In the EU nearly one in every five children was poor in 2008 (for the population as a whole the risk of poverty was around 17 per cent). The dimension of the problem and its consequences point out for the importance of knowing the processes behind it. This paper aims to investigate how labour market issues and public policies have been impact on child poverty, over recent years. Based on microdata gathered by the European Union Statistics on Income and Living Conditions (EU_SILC) for the period 2004-08 we give a portrait of child income poverty in European Southern countries such as: Italy, Portugal and Spain and also in Poland. Moreover, we investigate the major changes in social policies that could impact on child poverty such benefits target on family and child allowances. The international comparison will allow the identification of children’s poverty profile and pattern across the countries analysed and also design the different compositions between labour market elements / public policies in such countries. This exercise of comparison also enables a first test of the efficiency of these policies. The methodological framework used varies from descriptive methods to econometric models in order to sustain the discussion of the subject under study.
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