Parametric and semiparametric estimation of sample selection models: an empirical application to the female labour force in Portugal

This comment corrects the errors in the estimation process that appear in Martins (2001). The first error is in the parametric probit estimation, as the previously presented results do not maximize the log-likelihood function. In the global maximum more variables become significant. As for the semiparametric estimation method, the kernel function used in Martins (2001) can take on both positive and negative values, which implies that the participation probability estimates may be outside the interval [0,1]. We have solved the problem by applying local smoothing in the kernel estimation, as suggested by Klein and Spady (1993).

The role of central bank operating procedures in an economy with productive government spending

The choice of either the rate of monetary growth or the nominal interest rate as the instrument controlled by monetary authorities has both positive and normative implications for economic performance. We reexamine some of the issues related to the choice of the monetary policy instrument in a dynamic general equilibrium model exhibiting endogenous growth in which a fraction of productive government spending is financed by means of issuing currency. When we evaluate the performance of the two monetary instruments attending to the fluctuations of endogenous variables, we find that the inflation rate is less volatile under nominal interest rate targeting. Concerning the fluctuations of consumption and of the growth rate, both monetary policy instruments lead to statistically equivalent volatilities. Finally, we show that none of these two targeting procedures displays unambiguously higher welfare levels.

Allocative and productive efficiency in REE with asymetric information

We characterize the divergence between informational and economic efficiency in a rational expectations competitive market with asymmetric information about the costs of production. We find that prices may contain too much or too little information with respect to incentive efficient allocations depending on whether the main role of the price is, respectively, the traditional as index of scarcity or informational. Only when REE degenerate to Cournot equilibria the market solution does not show llocative inefficiency. With multidimensional uncertainty we find that the REE price does not have in general the incentive efficient information mix: It pays to sacrifice allocative efficiency at the REE to improve productive efficiency.

Productive efficiency and regulatory reform: The case of vehicle inspection services

Measuring productive efficiency provides information on the likely effects of regulatory reform. We present a Data Envelopment Analysis (DEA) of a sample of 38 vehicle inspection units under a concession regime, between the years 2000 and 2004. The differences in efficiency scores show the potential technical efficiency benefit of introducing some form of incentive regulation or of progressing towards liberalization. We also compute scale efficiency scores, showing that only units in territories with very low population density operate at a sub-optimal scale. Among those that operate at an optimal scale, there are significant differences in size; the largest ones operate in territories with the highest population density. This suggests that the introduction of new units in the most densely populated territories (a likely effect of some form of liberalization) would not be detrimental in terms of scale efficiency. We also find that inspection units belonging to a large, diversified firm show higher technical efficiency, reflecting economies of scale or scope at the firm level. Finally, we show that between 2002 and 2004, a period of high regulatory uncertainty in the sample’s region, technical change was almost zero. Regulatory reform should take due account of scale and diversification effects, while at the same time avoiding regulatory uncertainty.

The Security Council and the Legitimacy of the Use of Force: Legal, Normative, and Social Aspects.

Tal i com estableix la Carta de les Nacions Unides, el Consell de Seguretat determina l’existència d’una amenaça a la pau, un trencament de la pau o un acte d’agressió i decideix les mesures que han de fer-se servir per restaurar la pau i seguretat internacionals, també l’ús de la força. L’objectiu d’aquest article és explorar la legitimitat d’aquest ús de la força. Amb aquest objectiu, el text parteix d’una definició centrada en les seves dimensions legal, normativa i social. En segon lloc, s’analitzarà com aquestes dimensions estan representades als debats del Consell de Seguretat de la guerra d’Irak de 2003, un dels usos de la força més controvertits i que més debat ha generat als darrers anys. Finalment, l’anàlisi proposat permet treure algunes conclusions sobre les bases canviants de la legitimitat de l’ús de la força.

Primaries the unifying force

We present a formal model of intra-party politics to explain candidate selection within parties. We think of parties as heterogeneous groups of individuals who aim to implement a set of policies but who differ in their priorities. When party heterogeneity is too large, parties are in danger of splitting into smaller yet more homogeneous groups. In this context we argue that primaries can have a unifying role if the party elite cannot commit to policy concessions. Our model shows how alignment in the preferred policies of various factions within a party, the relative weight of each of these factions and the electoral system interact to create incentives for the adoption of primary elections. We discuss the existing empirical literature in the light of our theoretical predictions to provide a new, structured perspective on the adoption of primary elections.

Protective or counter-productive? Labor market institutions and the effect of immigration on EU natives

We estimate the effect of immigrant flows on native employment in WesternEurope, and then ask whether the employment consequences of immigrationvary with institutions that affect labor market flexibility. Reducedflexibility may protect natives from immigrant competition in the nearterm, but our theoretical framework suggests that reduced flexibility islikely to increase the negative impact of immigration on equilibriumemployment. In models without interactions, OLS estimates for a panel ofEuropean countries in the 1980s and 1990s show small, mostly negativeimmigration effects. To reduce bias from the possible endogeneity ofimmigration flows, we use the fact that many immigrants arriving after1991 were refugees from the Balkan wars. An IV strategy based onvariation in the number of immigrants from former Yugoslavia generateslarger though mostly insignificant negative estimates. We then estimatemodels allowing interactions between the employment response toimmigration and institutional characteristics including business entrycosts. These results, limited to the sample of native men, generallysuggest that reduced flexibility increases the negative impact ofimmigration. Many of the estimated interaction terms are significant,and imply a significant negative effect on employment in countrieswith restrictive institutions.

Informal care and labour force participation among middle-aged women in Spain

Informal care is today the form of support most commonly used by those who need other peoplein order to carry out certain activities that are considered basic (eating, dressing, taking a shower,etc.), in Spain and in most other countries in the region. The possible labour opportunity costsincurred by these informal carers, the vast majority of whom are middle-aged women, have not asyet been properly quantified in Spain. It is, however, crucially important to know these quantities ata time when public authorities appear to be determined to extend the coverage offered up to nowas regards long-term care.In this context, we use the Spanish subsample of the European Community Household Panel (1994-2001) to estimate a dynamic ordered probit and so attempt to examine the effects of various typesof informal care on labour behaviour. The results obtained indicate the existence of labouropportunity costs for those women who live with the dependent person they care for, but not forthose who care for someone outside the household. Furthermore, whereas caregiving for morethan a year has negative effects on labour force participation, the same cannot be said of those who start caregiving and stop caregiving .

Estudi tècnic-econòmic per a la instal·lació d'una granja d'ànecs per a producció de foie-gras situada en el terme municipal de Fontanals de Cerdanya

Inversors però, principalment professionals de l'àmbit agrari, per tal de buscar una diversificació de l'activitat agrícola i ramadera que desenvolupen a les seves finques, sobretot joves emprenedors, poden estar interessats en produccions alternatives com la producció d'ànecs per a foie-gras, per tal de complementar la seva renda agrària. Actualment cal augmentar la competitivitat de les finques agrícoles per tal que aquestes siguin econòmicament viables. L’objectiu de l'estudi és determinar la viabilitat econòmica d’una explotació ramadera d’ànecs per a la producció de foie-gras, en el terme municipal de Fontanals de Cerdanya, analitzant les diverses alternatives en quant a dimensionament i disseny de les instal·lacions, segons el cicle productiu de l’animal. L'alternativa escollida per realitzar l'estudi es la de semi-integració (cria, engreix i embocat), de règim semi-intensiu (durant l'etapa de l'engreix), amb animals mascles de la raça híbrida Mulard. Les instal·lacions tindran una capacitat de 6.500 animals, amb lots de 250 caps. Aquest dimensionament permet, durant la fase d'embocat, en la qual es requereix més dedicació, que la demanda de mà d'obra pugui ser satisfeta per un únic treballador. La principal conclusió que es pot extreure de l'estudi és que la inversió projectada és massa elevada i que aquesta econòmicament no és viable o rendible, ja que la despesa és massa elevada. Es mouen uns fluxos de caixa molt elevats i el marge comercial és molt reduït. Únicament si l'objectiu del promotor és obtenir una remuneració per la seva feina, sempre i quan és produeixi un augment del preu actual de la carn i una disminució del preu del pinso, es podria recomanar que es portés a terme la implantació de l'explotació, intentant, però, reduir la despesa d'execució de construccions i instal·lacions.

Declining labor force attachment and downward trends in unemployment and participation

The US labor market witnessed two apparently unrelated secular movements in thelast 30 years: a decline in unemployment between the early 1980s and the early 2000s,and a decline in participation since the early 2000s. Using CPS micro data and a stock-flow accounting framework, we show that a substantial, and hitherto unnoticed, factorbehind both trends is a decline in the share of nonparticipants who are at the margin ofparticipation. A lower share of marginal nonparticipants implies a lower unemploymentrate, because marginal nonparticipants enter the labor force mostly through unemployment,while other nonparticipants enter the labor force mostly through employment.

Fine-Tuning Translation Kinetics Selection as the Driving Force of Codon Usage Bias in the Hepatitis A Virus Capsid

Hepatitis A virus (HAV), the prototype of genus Hepatovirus, has several unique biological characteristics that distinguish it from other members of the Picornaviridae family. Among these, the need for an intact eIF4G factor for the initiation of translation results in an inability to shut down host protein synthesis by a mechanism similar to that of other picornaviruses. Consequently, HAV must inefficiently compete for the cellular translational machinery and this may explain its poor growth in cell culture. In this context of virus/cell competition, HAV has strategically adopted a naturally highly deoptimized codon usage with respect to that of its cellular host. With the aim to optimize its codon usage the virus was adapted to propagate in cells with impaired protein synthesis, in order to make tRNA pools more available for the virus. A significant loss of fitness was the immediate response to the adaptation process that was, however, later on recovered and more associated to a re-deoptimization rather than to an optimization of the codon usage specifically in the capsid coding region. These results exclude translation selection and instead suggest fine-tuning translation kinetics selection as the underlying mechanism of the codon usage bias in this specific genome region. Additionally, the results provide clear evidence of the Red Queen dynamics of evolution since the virus has very much evolved to re-adapt its codon usage to the environmental cellular changing conditions in order to recover the original fitness.

Filamin depletion blocks endoplasmic spreading and destabilizes force-bearing adhesions

Cell motility is an essential process that depends on a coherent, cross-linked actin cytoskeleton that physically coordinates the actions of numerous structural and signaling molecules. The actin cross-linking protein, filamin (Fln), has been implicated in the support of three-dimensional cortical actin networks capable of both maintaining cellular integrity and withstanding large forces. Although numerous studies have examined cells lacking one of the multiple Fln isoforms, compensatory mechanisms can mask novel phenotypes only observable by further Fln depletion. Indeed, shRNA-mediated knockdown of FlnA in FlnB¿/¿ mouse embryonic fibroblasts (MEFs) causes a novel endoplasmic spreading deficiency as detected by endoplasmic reticulum markers. Microtubule (MT) extension rates are also decreased but not by peripheral actin flow, because this is also decreased in the Fln-depleted system. Additionally, Fln-depleted MEFs exhibit decreased adhesion stability that appears in increased ruffling of the cell edge, reduced adhesion size, transient traction forces, and decreased stress fibers. FlnA¿/¿ MEFs, but not FlnB¿/¿ MEFs, also show a moderate defect in endoplasm spreading, characterized by initial extension followed by abrupt retractions and stress fiber fracture. FlnA localizes to actin linkages surrounding the endoplasm, adhesions, and stress fibers. Thus we suggest that Flns have a major role in the maintenance of actin-based mechanical linkages that enable endoplasmic spreading and MT extension as well as sustained traction forces and mature focal adhesions.