Immigration and the pension system in Spain

In this paper we use a large overlapping generations model with individuals that differ across age, productivity and native status to assess the effects on the pension system of different immigration quotas in the context of an aging population by computing how much should social security taxes be rised in order to pay for the pension burden in two model economies. The first one is the standard model pioneered by Auerbach and Kotlikoff (1987) where skilled and unskilled workers are perfect substitutes in the production process. In the second model economy, individuals with different skill levels are imperfect substitutes as in Canova and Ravn (1998). The main result of the paper is that half of the reduction of the social security tax rate associated with immigration in the standard model is lost when skilled and unskilled individual are imperfect substitutes. Consequently, the standard model with perfect substitution overestimates the ability of immigration inflows to sustain the pension system in Spain

Foreign direct investment and spillovers : gradualism may be better

In contrast to the standard literature, we show that the presence of spillovers may justify temporarily restricting the inflow of foreign direct investment. Our argument is based on two stylized features of spillovers: first, technology transfers --- and subsequent spillovers --- are limited by the economy's absorptive capacity; and second, spillovers take time to materialize. By letting capital in more gradually, initial investment has the time to create spillovers --- and upgrade the economy's absorptive capacity --- before further investment occurs. This allows subsequent capital inflows to benefit from greater technology transfers. As a result, the economy converges to a steady state with a superior technology and a greater capital stock.We acknowledge financial support from the European Union Directorate General XII (project SERD-1999-000102) and of the Comunidad de Madrid (project 06/0186/2002

Quantum localized states in photonic flat-band lattices

The localization of light in flat-band lattices has been recently proposed and experimentally demonstrated in several configurations, assuming a classical description of light. Here, we study the problem of light localization in the quantum regime. We focus on quasi one-dimensional and two-dimensional lattices which exhibit a perfect flat-band inside their linear spectrum. Localized quantum states are constructed as eigenstates of the interaction Hamiltonian with a vanishing eigenvalue and a well defined total photon number. These are superpositions of Fock states with probability amplitudes given by positive as well as negative square roots of multinomial coefficients. The classical picture can be recovered by considering poissonian superpositions of localized quantum states with different total photon number. We also study the separability properties of flat band quantum states and apply them to the transmission of information via multi-core fibers, where these states allow for the total passive suppression of photon crosstalk and exhibit robustness against photon losses. At the end, we propose a novel on-chip setup for the experimental preparation of localized quantum states of light for any number of photons.Comment: 12 pages, 5 figure

PRIVATIZING SOCIAL SECURITY: THE ROLE OF IMPERFECT SUBSTITUTION BETWEEN LESS AND MORE EXPERIENCED WORKERS

In this paper we use a large overlapping generations model with individuals that differ across age and productivity to assess the effect of privatizing a pay-as-you-go social security system in two model economies. The first one is the standard model pioneered by Auerbach and Kotlikoff (1987) characterized by the perfect substitutability in production of individuals with different experience levels. In the second one, individuals with different experience in the labor market are imperfect substitutes in production (Kremer and Thomson (1998)). The findings indicate that although in both economies the aggregate effects of removing social security are qualitatively similar, the standard model economy underestimates both the welfare losses of the individuals living at the period of the pension reform and the increase in pre-tax income inequality associated with such policy change.

ON THE INTERACTION BETWEEN EDUCATION AND SOCIAL SECURITY

This paper uses an overlapping generations model with endogenous fertility choices to analyze the quantitative costs and benefits of subsidizing higher education, paying particular attention to the interaction between such policy and the sustainability of the social security system. The paper focuses on the demographic change as the mechanism that link both policies. It is found that an increase in education subsidies changes the educational composition of the population and lowers average fertility. Lower average fertility and higher life expectancy of educated individuals translates into changes in the age structure of the population that requires an increase in the social security tax rate in order to balance the pension budget. Such process reduces the welfare benefits of this educational policy since the rise in social security taxes lowers the after-tax lifetime earnings of almost all individuals born in the period of the policy reform and over.

IMMIGRATION AND THE PENSION SYSTEM IN SPAIN

In this paper we use a large overlapping generations model with individuals that differ across age, productivity and native status to assess the effects on the pension system of different immigration quotas in the context of an aging population by computing how much should social security taxes be rised in order to pay for the pension burden in two model economies. The first one is the standard model pioneered by Auerbach and Kotlikoff (1987) where skilled and unskilled workers are perfect substitutes in the production process. In the second model economy, individuals with different skill levels are imperfect substitutes as in Canova and Ravn (1998). The main result of the paper is that half of the reduction of the social security tax rate associated with immigration in the standard model is lost when skilled and unskilled individual are imperfect substitutes. Consequently, the standard model with perfect substitution overestimates the ability of immigration inflows to sustain the pension system in Spain.

Ontological Reengineering for Reuse

This paper presents the concept of Ontological Reengineering as the process of retrieving and transforming a conceptual model of an existing and implemented ontology into a new, more correct and more complete conceptual model which is reimplemented. Three activities have been identified in this process: reverse engineering, restructuring and forward engineering. The aim of Reverse Engineering is to output a possible conceptual model on the basis of the code in which the ontology is implemented. The goal of Restructuring is to reorganize this initial conceptual model into a new conceptual model, which is built bearing in mind the use of the restructured ontology by the ontology/application that reuses it. Finally, the objective of Forward Engineering is output a new implementation of the ontology. The paper also discusses how the ontological reengineering process has been applied to the Standard-Units ontology [18], which is included in a Chemical-Elements [12] ontology. These two ontologies will be included in a Monatomic-Ions and Environmental-Pollutants ontologies