Quantile regression estimands and models: revisiting the motherhood wage penalty debate

This paper discusses the crucial but sometimes neglected differences between unconditional quantile regression (UQR) models and quantile treatment effects (QTE) models. We argue that there is a frequent mismatch between the aim of the quantile regression analysis and the quantitative toolkit used in much of the applied literature, including the motherhood wage penalty literature. This mismatch may result in wrong conclusions being drawn from the data, and in the end, misguided theories. In this paper, we clarify the crucial conceptual distinction between influences on quantiles of the overall distributions, which we term population-level influences, and individual-level QTEs. Further, we use data simulations to illustrate that various classes of quantile regression models may, in some instances, give entirely different conclusions (to different questions). Finally, we compare quantile regression estimates using real data examples, showing that UQR and QTE models differ sometimes but not always. Still, the conceptual and empirical distinctions between quantile regression models underline the need to match the correct model to the specific research questions. We conclude the paper with a few practical guidelines for researchers

Instrumentvariabler â en introduksjon for samfunnsforskere

En vanlig tilnærming for å identifisere kausale effekter i samfunnsvitenskapelig forskning er kontrollvariabelmetoden. Ofte er imidlertid én eller flere bakenforliggende variabler uobserverte, det er målefeil i variablene og/eller det er resiprok kausalitet. I disse tilfellene vil kontrollvariabelmetoden gi skjeve estimater. I denne artikkelen presenterer og diskuterer jeg en metode som kan benyttes for å unngå skjevhet som skyldes uobserverte variabler, målefeil og/eller resiprok kausalitet: instrumentvariabelmetoden. Målet med artikkelen er å gjøre leseren i stand til å vurdere validiteten av resultater i studier som bruker instrumentvariabler og identifisere variabler som kan benyttes som instrumenter i egen forskning. Diskusjonen vil vise at instrumentvariabelmetoden i teorien kan benyttes for å unngå skjevhet som skyldes korrelasjon mellom restleddet og forklaringsvariabelen, og derfor er et nyttig verktøy for å identifisere kausaleffekter. Det er imidlertid vanskelig å finne instrumenter som oppfyller alle forutsetningene i instrumentívariabelímetoden, og konsekvensene av brudd på forutsetningene er potensielt store. Et viktig poeng i artikkelen er derfor at vellykket bruk av instrumentvariabler krever en kreativ forsker som har en god forståelse av forskningsområdet

Do funds for more teachers improve student outcomes?

We investigate the effects of a large-scale Norwegian reform that provided extra teachers to 166 lower secondary schools with relatively high student-teacher ratios and low average grades. We exploit these two margins using a regression discontinuity setup and find that the reform reduced the student-teacher ratio by around 10% (from a base level of 22 students per teacher), with no crowding out of other school resources or parental support. However, the reform did not improve test scores and longer-term academic outcomes, and we can reject even small positive effects. We do find that the reform improved the school environment from the students’ perspective, but with the largest impact on aspects most weakly associated with better academic outcomes.Delfinansiert av Utdanningsdirektorate

Prevalence of sexual harassment among Norwegian female elite athletes in relation to sport type

Although it is often assumed that the prevalence of sexual harassment is different in different sports, this assumption has not been empirically tested. This study considers whether the experience of sexual harassment varies by sport. The female elite athletes (N = 553) in the study participated in 56 different sport disciplines. These were grouped as follows :1) team or individual sports; 2) extent to which clothing required for competition is revealing ; 3) gender structure (male-or female dominated membership statistics); and 4) gender culture (masculine, gender-neutral, or feminine). The data show that sexual harassment occurs in every sport group. Female elite athletes who participated in ‘masculine’ sports appear to experience more harassment than women in the other groups. We conclude that, when it comes to female athletes’ experiences of sexual harassment, sport type matters far less than sport participation per se

Sex Differences in Cannabinoid 1 vs. Cannabinoid 2 Receptor-Selective Antagonism of Antinociception Produced by Δ 9

The purpose of this study was to determine whether sex differ-ences in cannabinoid (CB)-induced antinociception and motoric effects can be attributed to differential activation of CB1 or CB2 receptors. Rats were injected intraperitoneally with vehicle, rimon-abant [5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-N-1-piperidinyl-1H-pyrazole-3-carboxamide (SR141716A), a putative CB1 receptor-selective antagonist; 0.1–10 mg/kg] or 5-(4-chloro-3-methylphenyl)-1-[(4-methylphenyl)methyl]-N-[(1S,2S,4R)-1,3,3-trimethylbicyclo[2.2.1]hept-2-yl]-1H-pyrazole-3-carboxamide (SR144528) (a putative CB2 receptor-selective antagonist; 1.0–10 mg/kg). Thirty minutes later, 9-tetrahydrocannabinol (THC; 1.25–40 mg/kg) or 5-(1,1-dimethylheptyl)-2-[5-hydroxy-2-(3-hydroxypropyl)cyclohexyl]phenol (CP55,940) (0.05–1.6 mg/kg) was injected. Paw pressure and tail withdrawal antinociception

Eating disorders in sport : current status and future directions in the study of the psychological factors

Este trabalho procura atingir dois objetivos. Em primeiro lugar, apresenta-se a situação atual da investigação sobre desordens alimentares no desporto. Neste caso, salientam-se as linhas de investigação dedicadas ao estudo da prevalência destes problemas no desporto e analisam-se as diferenças entre atletas e modalidades desportivas. Dadas as dificuldades destas linhas de investigação na compreensão dos comportamentos alimentares de risco nos atletas, são avançadas outras possibilidades de desenvolvimento da investigação. Assim, e enquanto segundo objetivo deste artigo, salientamos a necessidade dos estudos se dirigirem para a compreensão dos fatores psicológicos associados aos comportamentos alimentares de risco e implicados no desenvolvimento das desordens alimentares. Esta abordagem tem como vantagem adicional ajudar a prevenir estes problemas através da promoção das competências mentais dos atletas no sentido de resistirem melhor aos possíveis efeitos nocivos da prática desportiva, onde se inserem os problemas com a alimentação.This paper focuses on two main goals. In first place, we present the current status on the research about eating disorders in sport contexts. In this case, we point out studies dedicated to the analysis of the incidence of eating disorders in sport and studies that observe the differences between athletes and different sports in the tendency for these problems. Second, we proposed new research directions on this subject, namely the need of analysing the psychological factors that are related with the development of eating disorders on athletes. This research approach has the advantage of helping the prevention of eating disorders on athletes through the promotion of psychological skills that protect athletes from the negative effects of sport practicing, where are included maladaptive eating behaviors.(undefined

Diet matters, particularly in pregnancy – Results from MoBa studies of maternal diet and pregnancy outcomes

To access publisher's full text version of this article, please click on the hyperlink in Additional Links field or click on the hyperlink at the top of the page marked Files. This article is open access.Awareness that maternal diet may influence the outcome of pregnancy as well as the long-term health of mother and child has increased in recent years. A new food frequency questionnaire (FFQ) was developed and validated specifically for the Norwegian Mother and Child Cohort Study (MoBa). The MoBa FFQ is a semi-quantitative tool which covers the average intake of food, beverages and dietary supplements during the first 4 to 5 months of pregnancy. It includes questions about intakes of 255 foods and dishes and was used from 2002 onwards. Data assessed by the MoBa FFQ is available for 87,700 pregnancies. Numerous sub-studies have examined associations between dietary factors and health outcomes in MoBa. The aim of this paper is to summarize the results from 19 studies of maternal diet and pregnancy outcomes, which is the complete collection of studies based on the MoBa FFQ and published before September 2014. The overall research question is whether maternal diet – from single substances to dietary patterns – matters for pregnancy outcome. The pregnancy outcomes studied till now include birth size measures, infants being small and large for gestational age, pregnancy duration, preterm delivery, preeclampsia, as well as maternal gestational weight gain and postpartum weight retention. As a whole, the results from these studies corroborate that the current dietary recommendations to pregnant women are sound and that maternal diet during pregnancy is likely to contribute to reduce the risk of pregnancy complications including preterm birth, preeclampsia, and reduced foetal growth. The results provide supporting evidence for recommending pregnant women to consume vegetables, fruit, whole grain, fish, dairy, and water regularly and lower the intake of sugar sweetened beverages, processed meat products and salty snacks. The results showing negative impact of even low levels of environmental contaminants support the precautionary advice on consumption of foods containing these. New findings are that particularly lean fish explained the positive association between seafood intake and foetal growth, and the indications of a protective effect of probiotic and antimicrobial foods on pregnancy outcomes. This points to the importance of diet composition for a healthy gut flora and the body’s immune response. Although these studies are observational and cannot infer causality, the results identify diet as an important modifiable lifestyle factor, suggesting that healthy eating, defined as following the official recommendations, is particularly important in pregnanc

Systemic chemotherapy induces microsatellite instability in the peripheral blood mononuclear cells of breast cancer patients

INTRODUCTION: Systemic chemotherapy is an important part of treatment for breast cancer. We conducted the present study to evaluate whether systemic chemotherapy could produce microsatellite instability (MSI) in the peripheral blood mononuclear cell fraction of breast cancer patients. METHODS: We studied 119 sequential blood samples from 30 previously untreated breast cancer patients before, during and after chemotherapy. For comparison, we also evaluated 20 women who had no relevant medical history (control group). RESULTS: In 27 out of 30 patients we observed MSI in at least one sample, and six patients had loss of heterozygosity. We found a significant correlation between the number of MSI events per sample and chemotherapy with alkylating agents (P < 0.0001). We also observed an inverse correlation between the percentage of cells positive for hMSH2 and the number of MSI events per sample (P = 0.00019) and use of alkylating agents (P = 0.019). CONCLUSION: We conclude that systemic chemotherapy may induce MSI and loss of heterozygosity in peripheral blood mononuclear cells from breast cancer patients receiving alkylating agents, possibly mediated by a chemotherapy-induced decrease in the expression of hMSH2. These effects may be related to the generation of secondary leukaemia in some patients, and may also intensify the genetic instability of tumours and increase resistance to treatment