Paul Bingley

Comparison of academic performance of twins and singletons in adolescence: follow-up study

Objectives To determine whether twins in recent cohorts show similar academic performance in adolescence to singletons and to test the effect of birth weight on academic performance in twins and singletons. Design Follow-up study. Setting Denmark. Participants All twins (n=3411) and a 5% random sample of singletons (n=7796) born in Denmark during 1986-8. Main outcome measures Test scores in ninth grade (age 15 or 16), birth weight, gestational age at birth, parents age, and parents education. Results Ninth grade test scores were normally distributed, with almost identical mean and standard deviations for twins and singletons (8.02 v 8.02 and 1.05 v 1.06) despite the twins weighing on average 908 g (95% confidence interval 886 to 930 g) less than the singletons at birth. Controlling for birth weight, gestational age at birth, age at test, and parents age and education confirmed the similarity of test scores for twins and singletons (difference 0.04, 95% confidence interval −0.03 to 0.10). A significant, positive association between test score and birth weight was observed in both twins and singletons, but the size of the effect was small: 0.06-0.12 standard deviations for every kilogram increase in birth weight. Conclusions Although older cohorts of twins have been found to have lower mean IQ scores than singletons, twins in recent Danish cohorts show similar academic performance in adolescence to that of singletons. Birth weight has a minimal effect on academic performance in recent cohorts; for twins this effect is best judged relative to what is a normal birth weight for twins and not for singletons.

THE LABOUR SUPPLY, UNEMPLOYMENT AND PARTICIPATION OF LONE MOTHERS IN IN‐WORK TRANSFER PROGRAMMES*

In-work transfer schemes have recently been suggested as a device for encouraging labor force participation and reducing the severity of the disincentives associated with out-of-work income support schemes. Here the authors estimate a discrete choice labor supply model which allows for endogenous in-work welfare program participation. They also allow for involuntary unemployment so as to distinguish between program nonparticipation and an inability to obtain work and thereby generate an eligibility to the program. Copyright 1997 by Royal Economic Society.

Does more schooling reduce hospitalization and delay mortality? New evidence based on danish twins

Schooling generally is positively associated with better health-related outcomes—for example, less hospitalization and later mortality—but these associations do not measure whether schooling causes better health-related outcomes. Schooling may in part be a proxy for unobserved endowments—including family background and genetics—that both are correlated with schooling and have direct causal effects on these outcomes. This study addresses the schooling-health-gradient issue with twins methodology, using rich data from the Danish Twin Registry linked to population-based registries to minimize random and systematic measurement error biases. We find strong, significantly negative associations between schooling and hospitalization and mortality, but generally no causal effects of schooling.

The Danish Twin Registry: linking surveys, national registers, and biological information.

Over the last 60 years, the resources and the research in the Danish Twin Registry (DTR) have periodically been summarized. Here, we give a short overview of the DTR and a more comprehensive description of new developments in the twenty-first century. First, we outline our experience over the last decade of combining questionnaire and survey data with national demographic, social, and health registers in Statistics Denmark. Second, we describe our most recent data collection effort, which was conducted during the period 2008-2011 and included both in-person assessments of 14,000+ twins born 1931-1969 and sampling of biological material, hereby expanding and consolidating the DTR biobank. Third, two examples of intensively studied twin cohorts are given. The new developments in the DTR in the last decade have facilitated the ongoing research and laid the groundwork for new research directions.

The male-female health-survival paradox: a survey and register study of the impact of sex-specific selection and information bias.

PURPOSEnThis study examined whether the health-survival paradox could be due partially to sex-specific selection and information bias in surveys.nnnMETHODSnThe study is based on the linkage of three population-based surveys of 15,330 Danes aged 46-102 years with health registers covering the total Danish population regarding hospitalizations within the last 2 years and prescription medicine within 6 months before the baseline surveys.nnnRESULTSnMen had higher participation rates than women at all ages. Hospitalized women and women taking medications had higher participation rate compared with nonhospitalized women (difference=0.7%-3.0%) and female nonusers (difference=0.8%-7.6%), respectively, whereas no consistent pattern was found among men according to hospitalization or medication use status. Men used fewer medications than women, but they underreported medication use to a similar degree as did women.nnnCONCLUSIONSnHospitalized women, as well as women using prescription medicine, were slightly overrepresented in the surveys. Hence, the study found some evidence that selection bias in surveys may contribute to the explanation of the health-survival paradox, but its contribution is likely to be small. However, there was no evidence for sex-specific reporting of medication use among study participants.

Returns to tenure, firm‐specific human capital and worker heterogeneity

Workers with longer job tenure are paid more, on average, than those with shorter tenure. This paper re‐opens the debate about whether individual financial returns to tenure are due to firm‐specific human capital accumulation or sorting according to unobserved individual productivity heterogeneity. The paper constructs worker‐firm employment histories 1964‐1998 for all residents of Denmark and links this to wage and demographic information for all private sector workers 1980‐1998. All firm closures are observed, and following Kletzer we exploit these exogenous worker displacements from larger firms to distinguish between firm‐specific human capital and worker heterogeneity. Although the proportion of tenure returns due to firm‐specific human capital is smaller than that found in the USA, it has increased from 10 per cent in 1980 to 30 per cent in 1998 in Denmark. This change coincides with decentralisation of the wage bargaining process and may be explained by the increased freedom to write individual contracts.

Education and Cognitive Ability as Direct, Mediating, or Spurious Influences on Female Age at First Birth: Behavior Genetic Models Fit to Danish Twin Data

The authors study education and cognitive ability as predictors of female age at first birth (AFB), using monozygotic and dizygotic female twin pairs from the Middle‐Aged Danish Twin survey. Using mediated regression, they replicate findings linking education (and not cognitive ability) to AFB. But in a behavior genetic model, both relationships are absorbed within a latent variable measuring the shared family environment. Two interpretations are relevant. First, variance in AFB emerges from differences between families, not differences between sisters within the same family. Second, even in a natural laboratory sensitive to genetic variance in female fertility—during demographic transition—the variance in AFB was nongenetic, located instead within the shared environment.

Personnel policy and profit.

Abstract There is a growing awareness of large differences in worker turnover and pay between firms. However, there is little knowledge about the effects of this on firm performance. This paper describes how personnel policies with respect to pay, tenure, and worker flows are related to economic performance of the firm. Here we follow the population of 7118 medium- to large-sized private sector Danish firms over the period 1992–1995. In an instrumental variables framework, we use changes in the personnel composition of different firms operating in the same local labour market to provide exogenous identifying personnel structure variation. It is found that personnel policy is strongly related to economic performance. At the margin, more hires are associated with lower profit, and more separations with higher profit. For the average firm, one new job, all else equal, is associated with 2680 euros (2000 prices) lower annual profit. Higher wage level and lower wage growth are associated with higher profit. A workforce that has less tenure, all else equal, is more profitable.

The Incidence of Income Tax on Wages and Labour Supply

In the simple framework of a static model for equilibrium wages and labour supplies, we show that the incidence of income tax on equilibrium wages can be measured independently from the individual ...

The labour supply effects of a partial cash-out of in-kind transfers to single mothers

AbstractWe estimate a model of labour supply and participation in multiple cash and in-kind welfare programmes. The modeling exploits a reform that affected U.K. single mothers. In-work cash entitlements increased under this reform but eligibility to in-kind child nutrition programmes was lost for some households. When we allow for differences in the costs associated with each welfare programme we find that in-work cash and in-work in-kind transfers both have large positive labour supply effects. There is, however, a utility loss from programme participation which is estimated to be larger for the cash programme than for the child nutrition programmes. Our findings imply that the partial cash out of the in-kind transfers reduced labour supply and suggest that there may be a place in policy portfolios for in-kind programmes despite their “inefficiency”.JEL CodesC31, C35, D12, J22