REM - Artigos em Revistas Internacionais / Articles in International Journals
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- The mixed capacitated arc routing problem with non-overlapping routesPublication . Constantino, Miguel; Gouveia, Luís; Mourão, M. Cândida; Nunes, Ana CatarinaReal world applications for vehicle collection or delivery along streets usually lead to arc routing problems, with additional and complicating constraints. In this paper we focus on arc routing with an additional constraint to identify vehicle service routes with a limited number of shared nodes, i.e. vehicle service routes with a limited number of intersections. This constraint leads to solutions that are better shaped for real application purposes. We propose a new problem, the bounded overlapping MCARP (BCARP), which is defined as the mixed capacitated arc routing problem (MCARP) with an additional constraint imposing an upper bound on the number of nodes that are common to different routes. The best feasible upper bound is obtained from a modified MCARP in which the minimization criteria is given by the overlapping of the routes. We show how to compute this bound by solving a simpler problem. To obtain feasible solutions for the bigger instances of the BCARP heuristics are also proposed. Computational results taken from two well known instance sets show that, with only a small increase in total time traveled, the model BCARP produces solutions that are more attractive to implement in practice than those produced by the MCARP mode
- Sovereign debt composition and time-varying public finance sustainabilityPublication . Afonso, António; Jalles, João TovarWe compute time-varying responses of the sovereign debt ratio to primary budget balances for 13 advanced economies between 1980 and 2012, and assess how fiscal sustainability reacts to different characteristics of government debt. We find that the sustainability time-varying coefficient increases and countries become more fiscally sustainable if they contract a higher share of long-term public debt, if more debt is held by the central bank or if it is easily marketable in capital markets.
- The role of infrastructure efficiency in economic development—The case of underused highways in EuropePublication . Pontes, José Pedro; Pais, JoanaIn this paper, we establish a two-way causality between the phenomenon of infrastructure which is underused (the so-called “white elephant case”) and the aggregate productivity level (TFP) of the economy. On the one hand, the fact that a transport infrastructure is not used as much as it could be is itself a cause of low TFP because it represents low productivity for an important item of social capital. On the other hand, low aggregate productivity makes firms’ strategies founded on large scale of production and exports riskier, given the possibility that the political decision to build the required transport infrastructure may never be taken.
- Assessing the sustainability of external imbalances in the European UnionPublication . Afonso, António; Huart, Florence; Jalles, João Tovar; Stanek, PiotrExternal imbalances are a greater source of concern than public deficits and debts in some countries of the European Union, given their size and evolution. The new macroeconomic imbalance procedure (MIP), which aims at preventing these imbalances, relies on the surveillance of macroeconomic indicators. Some thresholds have been defined for the current account balance and the net international investment position (NIIP), but not for the NED which is taken as an auxiliary indicator in the MIP scoreboard. Prompted by these thresholds, we carried out an analysis of external debt sustainability of EU countries.
- ‘‘Whatever it takes” to resolve the European sovereign debt crisis? Bond pricing regime switches and monetary policy effectsPublication . Afonso, António; Arghyrou, Michael G.; Gadea, María Dolores; Kontonikas, AlexandrosThis paper investigates the role of unconventional monetary policy as a source of timevariation in the relationship between sovereign bond yield spreads and their fundamental determinants. We use a two-step empirical approach. First, we apply a time-varying parameter panel modelling framework to determine shifts in the pricing regime characterising sovereign bond markets in the euro area over the period January 1999 to July 2016. Second, we estimate the impact of ECB policy interventions on the time-varying risk factor sensitivities of spreads. Our results provide evidence of a new bond-pricing regime following the announcement of the Outright Monetary Transactions (OMT) programme in August 2012. This regime is characterised by a weakened link between spreads and fundamentals, but with higher spreads relative to the pre-crisis period and residual redenomination risk. We also find that unconventional monetary policy measures affect the pricing of sovereign risk not only directly, but also indirectly through changes in banking risk. Overall, the actions of the ECB have operated as catalysts for reversing the dynamics of the European sovereign debt crisis.
- Are scientific memes inherited differently from gendered authorship?Publication . Araújo, Tanya; Fontaínha, ElsaThis paper seeks to build upon the previous literature on gender aspects in research collaboration and knowledge diffusion. Our approach adds the meme inheritance notion to traditional citation analysis, as we investigate if scientific memes are inherited differently from gendered authorship. Since authors of scientific papers inherit knowledge from their cited authors, once authorship is gendered we are able to characterize the inheritance process with respect to the frequencies of memes and their propagation scores depending on the gender of the authors. By applying methods that enable the gender disambiguation of authors, missing data on the gender of citing and cited authors is dealt with. Our empirically based approach allows for investigating the combined effect of meme inheritance and gendered transmission. Results show that scientific memes do not spread differently from either male or female cited authors. Likewise, the memes that we analyse were not found to propagate more easily via male or female inheritance.
- Euro area sovereign yields and the power of unconventional monetary policyPublication . Afonso, António; Kazemi, MinaWe assess the determinants of long-term sovereign yield spreads, vis-à-vis Germany, using a panel of 10 Euro area countries over the period 1999.01–2016.07 notably regarding the ECB’s conventional and unconventional monetary policies. Our findings indicate that the international risk, the bid-ask spread and real effective exchange rate increased the 10-year sovereign bond yield spreads, while sovereign ratings’ improvements decreased the spreads. Moreover, Longer-term Refinancing Operations and the Securities Market Program decreased the yield spreads. The overall announcements of the unconventional policies also significantly decreased the yield spreads, notably in the periphery countries.
- Effects of euro area monetary policy on institutional sectors: the case of PortugalPublication . Afonso, António; Silva, JorgeWe study the effects of the euro area monetary policy on the institutional sectors in Portugal during the period 2000:4 2015:4. Our results show that the single monetary policy affected some variables that are proxies for the funding of each institutional sector of the economy: general government, other monetary financial institutions, non-financial corporations, households and the external sector. The period of the economic and financial adjustment programme influenced all institutional sectors, and financial integration in the euro area had an effect on the funding for the economy: there was a reduction of long term public debt to GDP ratio, external funding to the Portuguese other monetary financial institutions, and new loans to households.
- Tax structure for consumption and income inequality: an empirical assessmentPublication . Alves, José; Afonso, AntónioIn this study, we assess the relationship between several tax items and consumption and income inequality levels. For OECD countries between 1980 and 2015, we use panel data techniques and find tax threshold values regarding inequality levels and consumption. In particular, we obtain threshold values for social security contributions between 9.50 and 11.80% (of GDP), for long-run consumptions, while to promote a reduction in income inequalities we found a 15.51% share of social security contributions over GDP, in both short- and long-term perspectives. Lastly, our results would support higher taxes on firms, in GDP terms, to decrease income inequalities, although that might hamper aggregate consumption.
- The inversion of the spatial lag operator in binary choice models: Fast computation and a closed formula approximationPublication . Santos, Luís Silveira; Proença, IsabelThis paper presents a new method to approximate the inverse of the spatial lag operator, used in the estimation of spatial lag models for binary dependent variables. The related matrix operations are approximated as well. Closed formulas for the elements of the approximated matrices are deduced. A GMM estimator is also presented. This estimator is a variant of Klier and McMillen’s iterative GMM estimator. The approximated matrices are used in the gradients of the new iterative GMM procedure. Monte Carlo experiments suggest that the proposed approximation is accurate and allows to significantly reduce the computational complexity, and consequently the computational time, associated with the estimation of spatial binary choice models, especially for the case where the spatial weighting matrix is large and dense. Also, the simulation experiments suggest that the proposed iterative GMM estimator performs well in terms of bias and root mean square error and exhibits a minimum trade-off between computational time and unbiasedness within a class of spatial GMM estimators. Finally, the new iterative GMM estimator is applied to the analysis of competitiveness in the U.S. Metropolitan Statistical Areas. A new definition for binary competitiveness is introduced. The estimation of spatial and environmental effects are addressed as central issues.