Jesús Clemente

Testing for a Unit Root in Variables with a Double Change in the Mean

In this paper, we obtain a statistic that is useful for the analysis of the integration order of a variable which exhibits two changes in its mean. Our work begins by showing that the most commonly used unit root tests behave asymptotically in a correct manner for double changing mean variables. However, their use is not advisable in finite samples; rather, is better to design a new statistic which takes into account the presence of the two level shifts. We calculate the asymptotic distribution of this new statistic and tabulate it for several sample sizes using Monte Carlo methods. This new statistic allows us to show that the USA and UK real interest rates can be considered as stationary variables with a double shift in their mean.

Real exchange rates and structural breaks: evidence for the Spanish peseta

This paper analyses the fulfilment of the long-run PPP hypothesis between the Spanish Peseta and the currencies of the most important trade partners of the Spanish Economy. We show that the bilateral real exchange rate of the Spanish Peseta can be characterized as being stationary around a mean which exhibits some changes in its evolution.

Are the consumption/output and investment/output ratios stationary? An international analysis

This paper analyses the integration order of the consumption/output and investment/output ratios for a group of the most important OECD countries. Results show that these ratios can exhibit some structural breaks. Thus, the use of those statistics which do not take into account the presence of breaks leads to the acceptance of the unit root null hypothesis. A clear increase in the number of rejections of the unit root null hypothesis is found when these structural breaks are included in the model specification.

THE WAGE GAP BETWEEN COOPERATIVE AND CAPITALIST FIRMS: EVIDENCE FROM SPAIN

This paper analyses the differences between the wages received by workers in cooperative and capitalist firms in Spain using a sample constructed from administrative data. This paper shows that size and the sign of the wage gap depend on economic sector, type of cooperative and the wage distribution. This approach let us explain some contradictory results obtained in previous literature. Additionally, the wage gap decomposition used let us identify the causes for this gap.

Economic implications of labor induction

To assess health service costs associated with labor induction according to different clinical situations in a tertiary‐level hospital.

Government Social Spending and GDP: has there been a change in social policy?

Government Social Spending (GSS) is made up of a very heterogeneous range of variables, monetary transfers for retirement or illness, unemployment benefits, family services, active labour market policies and health expenditure. We believe that each of these components is of enormous importance to the economic development of a country. As has often been affirmed, however, GSS is one of the economic aggregates most sensitive to the ups and downs of economic growth. In moments of crisis, sharp cuts are almost immediate, and these may or may not be recovered when times are good. In this article, we examine the sensitivity of GSS to the evolution of Gross Domestic Product (GDP) in order to reveal the relationship between the two.

Scale and composition effects of human capital on Spanish regional migration

The aim of this article is to test the effects of human capital on Spanish internal migration, decomposed into two components: the size and the composition of the labour force. Our results indicate that those Spanish regions that experienced increases in the ratio of skilled to unskilled workers attracted less immigration in the period 1965 to 1984. Between 1985 and 2000, when employment rates turned nonsignificant in determining migration, the opposite was observed.

Linearization of a Radio-over-Fiber mobile fronthaul with feedback loop

The main disadvantage of Radio over Fiber (RoF) links digital predistortion (DPD) is that it is necessary to feedback the output signals at the Remote Radio Head (RRH) in a real scenario. Along the literature digital predistortion on RoF mobile fronthaul architectures considers an ideal feedback system, so it cannot be deployed in real systems. We propose the use of a RoF link to feedback these signals. This RoF link can be accomplished by an independent RoF link, in which the feedback signals are sent from the RRH to the Baseband Unit (BBU). Experiments are carried out with a 20MHz-LTE downlink signal (16QAM) at 2.65 GHz within the Band 7 of the LTE standard. The DPD performance has been tested in an intensity modulation/direct detection (IM/DD) RoF mobile fronthaul system. Experimental results reveal that with a properly postdistorter modeling of the feedback RoF link it is possible to achieve Adjacent Channel Power Ratio (ACPR) and Error Vector Magnitude (EVM) values close to the results with an ideal feedback link.

Digital predistortion of a full-duplex Radio-over-Fiber mobile fronthaul link with feedback loop

Radio over Fiber (RoF) fronthaul system linearization has become much more important due to the distortions produced by the optical link between the Baseband Unit (BBU) and the Remote Radio Head (RRH) in a Cloud Radio Access Network (C-RAN) architecture. Its main disadvantage is that in a real scenario the output signal may be far a few kilometers. Along the literature, digital predistortion (DPD) on RoF mobile fronthaul architectures considers an ideal feedback link, but in a real scenario the captured output signals at the BBU side are affected by the RoF feedback effects. In a first place, we evaluate the effects of this feedback loop on the downlink RoF predistorter. Then, we propose and experimentally demonstrate the use of a postdistorter on the feedback RoF in order to compensate its effects. This feedback RoF link can be accomplished in the same optical link by means of wavelength division-multiplexing (WDM). Experiments are carried out with a 20MHz-LTE downlink signal (16QAM) at 2.65 GHz within the Band 7 of the LTE standard. The DPD performance has been tested in an intensity modulation/direct detection (IM/DD) RoF mobile fronthaul system. Experimental results reveal that with a properly feedback RoF postdistortion it is possible to achieve Adjacent Channel Power Ratio (ACPR) and Error Vector Magnitude (EVM) values in the downlink RoF system close to the results with an ideal feedback link.

Predictors of perinatal outcomes and economic costs for late-term induction of labour

OBJECTIVE We aimed to predict the perinatal outcomes and costs of health services following labour induction for late-term pregnancies. MATERIALS AND METHODS We conducted a cohort study of 245 women who underwent labour induction during their 41st week of gestation. The cervical condition was assessed upon admission using the Bishop score and ultrasound cervical length measurements. We estimated the direct costs of labour induction, and a predictive model for perinatal outcomes was constructed using the decision tree analysis algorithm and a logit model. RESULTS A very unfavourable Bishop score at admission (Bishop score <2) (OR, 3.43 [95% CI, 1.77-6.59]), and a history of previous caesarean section (OR, 7.72 [95% CI, 2.43-24.43]) or previous vaginal delivery (OR, 0.24 [95% CI, 0.09-0.58]) were the only variables with predictive capacity for caesarean section in our model. The mean cost of labour induction was €3465.56 (95% confidence interval [CI], 3339.53-3591.58). Unfavourable Bishop scores upon admission and no history of previous deliveries significantly increased the cost of labour induction. Both of these criteria significantly predicted the likelihood of a caesarean section in the decision tree analysis. CONCLUSION The cost of labour induction mostly depends on the likelihood of successful trial of labour. Combined use of the Bishop score and previous vaginal or caesarean deliveries improves the ability to predict the likelihood of a caesarean section and the economic costs associated with labour induction for late-term pregnancies. This information is useful for patient counselling.