21 Feb
Docentbevis Rense Nieuwenhuis

Appointment to associate professor: my application

I was appointed to associate professor in sociology, by Stockholm University, on February 19 2018. In Sweden, one applies for the title of ‘Docent’, which corresponds to associate professor. The application, as well as 10 publications, are evaluated by an internal and an external reviewer. Based on their report, a commission decides based on research and teaching qualifications.

This is quite a lengthy process, and although I wrote my application before last summer, I thought it would be interesting to share the main body of my application. In true Swedish fashion where the application and the reviewer reports will be made public anyway. It describes four research lines that I have developed.

I am truly grateful of the support I continue to experience at the Swedish Institute for Social Research (SOFI), and the opportunity to collaborate with many great academics.

Application to associate professor

Rense Nieuwenhuis is a quantitative sociologist, interested in how social policy developments and demographic trends affect in economic inequality. Almost all of his studies are country-comparative in nature. With respect to social policy, he has mainly focused on family policies. Recently, more attention has been given to the European Commission’s social investment perspective, including the turn towards active labour market policies. In terms of demographic trends, his focus has been on trends in motherhood, educational expansion and homogamy, and single parenthood. Outcomes of interest were gendered differences in employment, poverty, and income inequality. Nieuwenhuis has developed three main research lines answering questions pertaining to the interplay between social policy developments and demographic trends, and one research line on methodological tools that help address the substantive questions. These research lines are detailed below.

The overview below includes a selection of 10 studies (referenced below). These include his dissertation, 7 studies in international peer-reviewed journals, and two chapters from a book he co-edited. The seven studies in his dissertation are discussed separately, with reference to the dissertation (#1). Most of these are now published in peer-reviewed journals.

In addition to developing these research lines, Nieuwenhuis is an active member of the academic community. He co-edited a forthcoming book on single parents, bringing together over 30 international scholars and coordinating their contributions to timely completion. He is often invited to give talks about his work, for research visits, and to teach at summer schools. He was commissioned to do work for the DG Employment of the European Commission, the European Institute for Gender Equality (EIGE), and the United Nations Entity for Gender Equality and the Empowerment of Women (UN-Women). He is also actively involved in the InGRID-2 project, which is a major EU Horizon 2020 funded initiative.

Combining institutional and demographic explanations

Nieuwenhuis’ first research line was developed in his PhD dissertation (#1), which was titled “Family Policy Outcomes: Combining institutional and demographic explanations of women’s employment and earnings inequality in OECD countries, 1975-2005″. In his dissertation, the argument was developed that the combination of institutional explanations and demographic explanations of women’s employment is more informative than a mere reference to determinants of either of these different strands of explanation. Institutional explanations have predominantly been invoked to help understand differences in women’s employment across countries, or trends in their employment, based on inter-country differences in the context in which women make their employment-related decisions. Demographic explanations have predominantly been invoked to understand differences in employment rates between women with a different demographic background within a single country. Combining these two strands of explanation not only provides a more detailed explanation of country-differences in economic inequality, it also provides the opportunity to address economic disparities between individuals with a different demographic, or socio-economic, background. In other words, it points towards institutional explanations of inequalities between demographic (and socio-economic) groups within societies, as well as to possible explanations of variation in the magnitude of such demographic inequalities across countries.

In the first empirical chapter of his dissertation (#1, also published), “Institutional and Demographic Explanations of Women’s Employment in 18 OECD countries, 1975-1999″, the first empirical support was provided. The article showed the importance of a wide range of institutional determinants, including several family policies and labour market characteristics such as unemployment and service sector size. Demographic determinants of women’s employment were covered by showing higher employment among women of younger generations, with higher levels of education, without a partner, and women without children. The multilevel design allowed to assess trends of the ‘motherhood-employment gap’ within countries over time, and to show how most work-family reconciliation policies (maternity leave, childcare leave, pay during leave) were beneficial to mothers but did not affect the employment of women without children. By differentiating between mothers and women without children, this was one of the first studies to convincingly demonstrate that financial support policies to families with children, measured as generous family allowances, are associated with reduced employment rates among women. The importance of combining institutional and demographic explanations was further demonstrated in Chapter 3 of Nieuwenhuis’ dissertation (#1) titled “Stratified Outcomes of Family Policies”, that found that work-family policies were particularly effective in closing the motherhood-employment gap (i.e. the difference in employment between mothers and women without children) among higher educated women. Such ‘Matthew effects’ could not have been found using institutional approaches alone. In chapter 4 of his dissertation (“Is these such a thing as too long childcare leave?”, (#1, also published), the question whether very long periods of childcare leave can have negative outcomes for women’s employment was revisited. In this study, it was argued and demonstrated that to correctly answer this question, one should combine both institutional and demographic indicators of women’s employment. Doing so, it was indeed found that very long periods of childcare leave reduce the employment of mothers but not of women without children, even while accounting for various demographic and institutional control variables.

Other studies in this research line include a study with Mark Levels and colleagues (#2) on how changes in Dutch legislation on contraceptives and induced abortion have affected prevalence of unintended pregnancies and women’s decisions regarding induced abortion by level of education. Unintended pregnancies were less likely when contraceptives were legal and available, and when abortion was legal and abortion services were available, women were more likely to abort an unintended pregnancy. The results further showed that higher educated women are less likely to experience an unintended pregnancy, but condition on having an unintended pregnancy higher educated women were more likely to choose for an abortion. Together with Andringa and Van Gerven (#3) it was shown how the absence of public childcare negatively affects maternal employment, and particularly so among women with traditional gender role attitudes.

Single-parent poverty and well-being

The second research line, developed after completing my dissertation, focuses on the interplay between social policy and a particular demographic trend: the rising number of single-parent families. This research line was developed together with Laurie C. Maldonado, starting with a study (#4) on how family policies might impact poverty risk of single-parent families differently from two-parent families. The study covered 18 OECD countries from 1978 to 2008. Along the line of Nieuwenhuis’ earlier research, a distinction was made between work-family reconciliation policies (e.g. paid leave) and financial support policies (e.g. family allowances). It was shown that both types of family policies reduce poverty among single-parent families, and that work-family reconciliation policies operate by facilitating employment particularly among single-parent families. Earnings from this employment helped to reduce poverty. In a follow-up article (#4), the importance and feasibility of stimulating employment among single-parent families was interpreted from the perspective of the European Social Investment paradigm. It was argued that policies that ‘prepare’ families to reduce poverty by means of employment can be beneficial for single-parent families, yet that many single-parent families live in poverty even while employed. This means that financial support policies that ‘repair’ poor economic outcomes, such as family allowances, cannot not be abandoned without increasing poverty risks for single parents.

In a forthcoming book chapter (#6) it was found that poverty among working single parents is very common. Three distinct patterns of performance were distinguished in how countries approach in-work poverty among single parents: A balanced approach of ensuring low inequality on the labour market combined with redistribution, an unbalanced approach of combating in-work poverty mostly through redistribution, and an approach in which high inequality on the labour market is compensated with redistributive policies only to a very limited extent. Countries that rely on a balanced approach to reduce inequality on the labour market, both with respect to class and gender, combined with an adequate level of redistribution, seem best situated for a durable reduction of poverty among working single parents.

Nieuwenhuis organised (with Maldonado) a total of five panels on single parents at three international conferences (Work and Family Researchers Network in New York, ESPAnet in Odense, and Policy & Politics in Bristol). Based on the contributions in these panels, as well as including contributions from other experts, Nieuwenhuis co-edited a book on single parents. In the introduction chapter of this book (#9), the theoretical concept of “the triple bind of single-parent families” is introduced: single parents and their families face higher risks of impaired socio-economic well-being, because of the combination of (1.) inadequate resources, (2.) inadequate employment, and (3.) inadequate policies. The importance and interplay of each of these three inadequacies was empirically demonstrated in the book. As an example, in an empirical chapter (#10) by Nieuwenhuis (with Tøge and Palme) the impact of employment and social policy on the health of single parents is analysed. The chapter finds that single parents are in better health when they are employed, and when their level of education is higher. Active labour market policies and public childcare benefit the health of single parents in two ways: by increasing their likelihood of being employment, and by benefitting the health of those who are employed (for instance, by reducing their work-family imbalance). Yet, the policies were also found to be associated with worse health among those who are not employed, suggesting selection effects. Financial transfer policies, measured as social assistance and financial supplements to families with children, were found to benefit the health of the non-employed.

The impact of rising women’s employment on inequality & poverty

The third research line addresses questions pertaining to how changes in female labour force participation have affected trends in economic inequality and poverty. It was argued (elsewhere) that an increase in women’s employment contributed to more income inequality between households, because spouses’ incomes (within households) are positively correlated. In other words, because higher earning men tend to be married to higher earning women, rising female labour force participation was argued to increase income inequality between households. Nieuwenhuis, however, showed with Van der Kolk and Need (Chapter “Earnings inequality within and between households” in dissertation #1, now published) that this is not the case. Indeed, with higher rates of women’s employment, the positive correlation between spouses’ incomes was more strongly positive, and this made a small contribution to higher income inequality between households. However, it was also found that rising employment rates of women resulted in a reduction of income inequality among women, which in turn strongly reduced income inequality between households. The latter effect was found to be stronger. Therefore, the net effect of increasing women’s employment rates, and thus of an (a.) increased correlation between spouses’ earnings and (b.) reduced income inequality among women, was found to be a sizeable reduction of income inequality between households. In a second study (Chapter “Family Policies and Earnings Inequality Between Households” in dissertation #1), it was found that women’s employment more strongly reduced income inequality between households in societies with generous work-family reconciliation policies, and with limited family allowances. This links this research line back to Nieuwenhuis’ first one on combining institutional and demographic explanations of inequality. The relevance of this finding is that it shows that, in contrast to various arguments in the literature, family policy arrangements that stimulate women’s employment are not at odds with low levels of income inequality between households. Currently, Nieuwenhuis (with Van Lancker, Collado & Cantillon, not included as appendix) works on study examining the impact of rising female labour force participation on trends in household poverty. The findings indicate that this impact, at best, has been moderate. Moreover, in many countries female labour force participation rates seem to have hit some form of a ceiling, not increasing any further. This has important implications for social policy goals set by the European Commission, as it limits the potential for reducing poverty by stimulating women’s employment.

Statistical Methods

Nieuwenhuis developed a methodological research line to support the three research lines above, by developing the statistical tools required to answer the country-comparative research questions central to his research.

Nieuwenhuis developed (with Te Grotenhuis and Pelzer) statistical software that provides statistical diagnostics with respect to influential cases in multilevel regression models, and published an article on this software package (chapter “Influence.ME: Tools for detecting influential data in multilevel regression models” in dissertation #1, also published). The importance of this highly cited article lies in the fact that multilevel models in country-comparative research often face the challenge of a relatively small number of countries included in the analyses. Such models can be severely biased because of a single country being a strong outlier / influential case. This software helps to assess and prevent such bias.

As much of the research is about comparing measures of economic inequality across countries, tools had to be developed to make such income datasets comparable across countries (in technical terms: measurement equivalent). Although the data in the LIS Database that he used are mostly comparable across countries, issues of comparability arose when comparing income of spouses in a country-comparative study. Tools had to be developed to allow for such comparisons, and an evaluation of these tools was accepted for publication (In Chapter “Comparative analyses of gross and net earnings” in dissertation #1, also published).

When applying regression models to categorical (independent) variables, dummy variables are often used. A disadvantage of the traditional way in which dummy are created, is that a specific reference category has to be chosen. An alternative was developed, called ‘weighted effect coding’. With weighted effect coding, the effect for each category represents the deviation of that category from the weighted mean (which corresponds to the sample mean). This technique has particularly attractive properties when analysing observational data, that commonly are unbalanced. This technique was described in publication #7, and Nieuwenhuis developed the statistical software to apply weighted effect coding in generalised linear regression models. In subsequent publications, the mathematical procedures were extended to allow for the interaction between categorical variables and for the interaction between a categorical variable and a continuous variable (#8). These are novel methods, and neither the mathematical procedure for the interactions, nor the application in statistical software were available.


  1. Nieuwenhuis, R. (2014). Family Policy Outcomes: Combining Institutional and Demographic Explanations of Women’s Employment and Earnings Inequality in OECD Countries, 1975-2005. PhD Dissertation, University of Twente.
  2. Levels, M., A. Need, R. Nieuwenhuis, R. Sluiter, and W. Ultee (2012). Unintended Pregnancy and Induced Abortion in the Netherlands 1954-2002. European Sociological Review 28, 301-318.
  3. Andringa, W., R. Nieuwenhuis, and M. Van Gerven (2015). Women’s working hours: the interplay between gender role attitudes, motherhood, and public childcare support in 23 European countries. International Journal of Sociology and Social Policy 35(9/10), 582-599.
  4. Maldonado, L. C. and R. Nieuwenhuis (2015). Family Policies and Single-Parent Poverty in 18 OECD Countries, 1978-2008. Community, Work and Family 18(4), 395-415.
  5. Nieuwenhuis, R. and L. C. Maldonado (2015). Prepare versus Repair? Combining parental leave and family allowances for social investment against single-parent poverty. Belgisch Tijdschrift voor Sociale Zekerheid (Belgian Review of Social Security) 57(1), 115-123.
  6. Nieuwenhuis, R. and L. C. Maldonado (2018). Single-Parent Families and In-Work Poverty. In: Handbook of Research on In-Work Poverty. Ed. by H. Lohmann and I. Marx. Edward Elgar.
  7. Grotenhuis, M. te, B. Pelzer, A. Schmidt-Catran, R. Nieuwenhuis, R. Konig, and R. Eisinga (2017). When size matters: advantages of weighted effect coding in observational studies. International Journal of Public Health, 62(1), pp. 163-167.
  8. Nieuwenhuis, R., M. Te Grotenhuis, and B. Pelzer (2017). Weighted Effect Coding for Observational Data with wec, R Journal, 9(1), pp. 477-485.
  9. Nieuwenhuis, R. and L.C. Maldonado (2018). The Triple Bind of Single-Parent Families: resources, employment, and policies. In Nieuwenhuis, R. and L.C. Maldonado (eds). The Triple Bind of Single-Parent Families: resources, employment and policy to improve well-being. Bristol: Policy Press.
  10. Nieuwenhuis, R., Tøge, A-G., Palme, J. (2018). The health penalty of single parents in institutional context. In Nieuwenhuis, R. and L.C. Maldonado (eds). The Triple Bind of Single-Parent Families: resources, employment and policy to improve well-being . Bristol: Policy Press.
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