Jeroen Smits

Twinning across the Developing World

Background Until now, little was known about the variation in incidence of twin births across developing countries, because national representative data was lacking. This study provides the first comprehensive overview of national twinning rates across the developing world on the basis of reliable survey data. Methods Data on incidence of twinning was extracted from birth histories of women aged 15–49 interviewed in 150 Demographic and Health Surveys, held between 1987 and 2010 in 75 low and middle income countries. During the interview, information on all live births experienced by the women was recorded, including whether it was a singleton or multiple birth. Information was available for 2.47 million births experienced by 1.38 million women in a period of ten years before the interview. Twinning incidence was measured as the number of twin births per thousand births. Data for China were computed on the basis of published figures from the 1990 census. Both natural and age-standardized twinning rates are presented. Results/Conclusions The very low natural twinning rates of 6–9 per thousand births previously observed in some East Asian countries turn out to be the dominant pattern in the whole South and South-East Asian region. Very high twinning rates of above 18 per thousand are not restricted to Nigeria (until now seen as the worlds twinning champion) but found in most Central-African countries. Twinning rates in Latin America turn out to be as low as those in Asia. Changes over time are small and not in a specific direction. Significance We provide the most complete and comparable overview of twinning rates across the developing world currently possible.

Length of life inequality around the globe

Inequality in the distribution of adult length of life - defined as age at death in the population aged 15 and over - is studied for virtually all countries of the world using a new database with over 9000 life tables covering a period of up to two centuries. The data reveal huge variation among countries and time periods in the degree to which the available years of life are distributed equally among the population. Most length of life inequality (about 90%) is within-country inequality. Our findings make clear that measures of length of life inequality should be adjusted for life expectancy to get a more relevant indicator of length of life differentials across populations. At similar levels of life expectancy, substantial differences in inequality are observed, even among highly developed countries. Expressed as premature mortality, inequality may be 35-70% higher in the most unequal countries compared to the most equal ones. Countries that reached a certain level of life expectancy earlier in time than other countries, and countries that improved their life expectancy more quickly than others, experienced higher levels of inequality.

Socioeconomic variations in the course of stroke: unequal health outcomes, equal care?

Study objective: The aim of this paper is to quantify the socioeconomic gap in long term health outcomes after stroke and related health care utilisation, in order to evaluate whether those in need of care do actually receive appropriate levels of care. Design: Stroke patients from the lower socioeconomic group were compared with stroke patients from the higher socioeconomic group with respect to sociodemographic and clinical characteristics, health outcomes, and related health care utilisation. Setting: Patients were recruited from admissions to 23 randomly selected hospitals in the Netherlands. Patients: 465 patients were included who had had a stroke six months earlier and were followed up three years and five years after stroke. Main results: The observed odds ratios suggest that patients from the lower socioeconomic group experienced more disabilities up to three years after stroke and more handicaps up to five years after stroke. After adjusting for health care needs there were no significant associations between socioeconomic status and health care utilisation. The observed figures, however, suggest that a lower socioeconomic status tended to increase admission to nursing homes and to decrease receiving care in non-institutional settings. Conclusions: Overall, inequalities in long term health outcomes were observed but solid indications for large inequalities in health care utilisation were not found. More investments in coordinated stroke services are needed to alleviate the unfavourable health situation of disadvantaged groups and to ensure that health care services respond appropriately to the health care needs of different socioeconomic groups.

Five decades of educational assortative mating in 10 East Asian societies

We study trends in educational homogamy at six boundaries in the educational structure of 10 East-Asian societies and explain its variation using explanatory variables at the country, cohort and boundary level. Educational homogamy was higher at the higher boundaries in the educational structure. Since the 1950s it decreased at all but the lowest boundaries, indicating convergence to a relatively low level of homogamy. Educational homogamy is lower in societies that are more modern, have higher female employment and experienced less Confucian influence. Results support the general openness and the exclusivity hypothesis, which predict educational homogamy to decrease in modernizing societies and to be higher when the group of more highly educated is smaller. Findings suggest that the trend towards less educational homogamy is related to educational expansion.

Career Migration, Self-selection and the Earnings of Married Men and Women in the Netherlands, 1981-93

The relationship between career migration and earnings is studied for married men and women in the Netherlands. The hourly wages of married men and women who made a recent long-distance move are found to be higher than those of married men and women who did not move or who moved only over a small distance. This earning difference between migrants and non-migrants seems to be due completely to the fact that the migrants are a favourable self-selected group, both with regard to their measured characteristics and with regard to their unmeasured characteristics. If this favourable self-selection is taken into account, the male and female migrants turn out to earn significantly less than their non-migrating counterparts. For the males, this finding suggests that before the move they were in relatively unfavourable labour market situations compared with the non-migrants with the same measured and unmeasured characteristics. For the females, the negative effect of migration merely indicates that most long-distance moves are still made for the career of their husband.

Maternal height and child mortality in 42 developing countries

Previous research reports mixed results about the association between maternal height and child mortality. Some studies suggest that the negative association might be stronger in contexts with fewer resources. This hypothesis has yet not been tested in a cross‐nationally comparative design. We use data on 307,223 children born to 194,835 women in 444 districts of 42 developing countries to estimate the association between maternal height and child mortality and test whether this association is modified by indicators at the level of the household (like sex, age and twin status of the child and socio‐economic characteristics of the mother and her partner), district (regional level of development, public health facilities and female occupational attainment) and country (GDP per capita). We find a robust negative effect of logged maternal height on child mortality. The effect of maternal health is strongest for women with least education and is more important in the first year after birth and for twin births. The indicators of development at the district and country level do not modify the effect of maternal height. Am. J. Hum. Biol. 2009.

Linguistic capital: Language as a socio-economic resource among Kurdish and Arabic women in Turkey

Data from the 1998 Turkish Demographic and Health Survey are used to gain insight into the characteristics of the non-Turkish speaking individuals in Turkey and in the socio-economic consequences of not speaking Turkish for them. The very large majority of non-Turkish speaking individuals turn out to be Kurdish and Arabic women, living in East Turkey and in the countryside. The data indicate that of the married women aged 15–49 in Turkey, about 4 per cent, or one in 25, is not able to speak Turkish. More than 90 per cent of these women has not finished primary education. Regarding their social background, our results suggest that they were more under the influence of traditional cultural values, that their access to the public domain was limited, and that they were more heavily controlled by their family. Regarding the consequences of not speaking Turkish, we found the non-Turkish speaking women to be less employed in the formal economy, to have husbands with lower educational levels and occupations and to have lower family incomes. This result is in line with the predictions of linguistic capital theory.

Ethnic Intermarriage in Times of Social Change: The Case of Latvia

We gain insight into the dynamics of ethnic intermarriage in times of social change by studying marriages between Latvians and Russians (including Belarussians and Ukrainians) that occurred in Latvia before and after independence from the Soviet Union. Before independence, ethnic intermarriage was already rather common, involving about 17% of the marriages annually. Since independence, intermarriage between Russians and Latvians has increased substantially. Part of this increase can be explained by selective emigration, but at least half of it may be due to integrative processes. Although there were more marriages between Russian men and Latvian women before independence, the gender pattern reversed after independence. Intermarriage levels were the highest among the less educated, children of mixed couples, partners with similar educational levels, and people in the countryside.

Migration of Couples with Non- Employed and Employed Wives in the Netherlands: The Changing Effects of the Partners' Characteristics

Data for 1977 and 1995/96 are used to study (changes in) the effects of the partners’ resources on long‐distance migration of couples in the Netherlands. The analyses were performed separately for couples with employed and with non‐employed women. In 1977, couples with non‐employed women showed the classical pattern of family migration, with strong effects of the human capital and labour market characteristics of the male and the females mostly using their power to prevent migration. The couples with employed women, on the other hand, in 1977 already showed a more modern pattern of family migration. The effects of the male’s occupational prestige and sector were not significant for these couples and an age advantage of the male did not lead to more migration. Over time, the position of the employed women seems to have become even stronger and our results suggest that in 1996 at least some of them were able to initiate a move for their own career and hence to turn their husband into a tied mover.

Socioeconomic status of very small areas and stroke incidence in the Netherlands

Objective: To examine whether characteristics of very small living areas can be used to predict disease incidence and to use these characteristics to assess socioeconomic differences in stroke incidence in the Netherlands. Design: Characteristics of postcode areas of stroke patients are compared with characteristics of postcode areas of all individual people in the study region, using Poisson regression analysis. Setting: Six provinces of the Netherlands, covering about half of the country. Patients: 760 patients who in 1991 or 1992 were consecutively admitted because of stroke to 23 Dutch hospitals. Main results: Stroke incidence is significantly higher among people living in postcode areas with below average socioeconomic status (relative risk=1.27; 95% confidence intervals 1.08 to 1.51) and among people living in postcode areas with predominantly older inhabitants (RR=3.17; 95% CI=2.29 to 4.39). It is also significantly increased in more urbanised areas compared with the countryside, the highest incidence being found in the large cities (RR=1.78; 95% CI=1.31 to 2.44). Conclusions: A clear socioeconomic gradient in stroke incidence in the Netherlands is observed, with people living in detailed postcode areas with below average socioeconomic status experiencing a significantly higher risk of stroke. The analysis also confirms that characteristics of detailed postcode areas can effectively be used to differentiate between areas with and areas without stroke patients.