Skip to content

Research Paper IFS Briefing Notes BN223

Wage progression and the gender wage gap: the causal impact of hours of work


Publication date

Feb 2018


In the early 1990s, average hourly wages were almost 30% lower for women than for men. The gender wage gap has come down, but it remains at around 20%. There are lots of reasons for the scale and persistence of this gap, but new work, funded by the Joseph Rowntree Foundation shows that one important factor is that mothers spend less time in paid work, and more time working part-time, than do fathers. As a result, they miss out on earnings growth associated with more experience.
Reducing differences in wages between men and women is high on the political agenda, as evidenced by the quotations above. Understanding these differences is important not only from the point of view of gender equality per se, but also for how best to address low pay and a lack of wage progression more generally. Poverty is increasingly a problem of low pay rather than lack of employment. The proportion of people in paid work has reached record levels, with female employment having risen especially quickly over the last 25 years, and two-thirds of children in poverty now live in a household with someone in paid work. Understanding the wage gap between men and women is important in its own right, but all the more so now that so many families are left in poverty as a result of low wages.
In principle, there are many reasons why the wages of male and female workers might be different: to name a few of the possibilities, they could have different levels of education or labour market experience; they could be in different kinds of jobs offering different balances between financial benefits (such as wages) on the one hand and other benefits (such as flexibility in hours) on the other; they could be working in different local labour markets, with different degrees of competition for workers between employers, putting different amounts of upward pressure on wages; they could bargain differently over their wages; or there could be outright discrimination. The potential underlying causes of those differences are also wide-ranging. Men and women can make choices about their jobs and careers, which will depend on their preferences; but they can also face different constraints. For example, the division of childcare responsibilities within the home can clearly shape the kinds of jobs and career choices that are open to different members of the household.
It would be very difficult for one study to disentangle robustly all of these mechanisms simultaneously – or at least, that is beyond the current frontier of social science. But making progress on these questions is crucial for knowing how public policy should best respond. This briefing note provides an accessible summary of a new IFS working paper on this topic. The main contributions of the paper are: to isolate the causal role of full-time and part-time experience in determining the wages of men and women; to draw out the implications for what these experience differences can and cannot explain about the gender wage gap over the life cycle; and to examine how this differs for different groups of men and women (in particular, the low- versus high-educated). This exercise does not reveal why the experience differences between men and women arise in the first place. These differences may themselves be caused by other inequalities, such as social norms towards unequal division of childcare or other home responsibilities. But by obtaining robust estimates of what can and cannot be explained by experience differences – however they arise – we can provide a sense of scale for how much of the gender wage gap policymakers could reasonably expect to tackle, were they to focus on factors that can affect the build-up of labour market experience.
The role of experience in paid work – given its association with wages – is an oft-discussed driver of the gender wage gap. But studies typically suffer from a methodological problem: people with different levels of labour market experience may be different from each other in all sorts of other ways that are difficult to control for, meaning that researchers risk bundling up the actual causal impact of experience with the impacts of other factors that also affect wages or wage progression. In the new working paper, we employ a technique to get around this problem and identify the impact of labour market experience in driving the observed gender wage gap.
The structure of this briefing note is as follows. In Section 1, we set out the context of wages for male and female workers, how they differ according to education level and how the gap has evolved over time. In Section 2, we show how differences in wages between men and women evolve over the life cycle, and relate this in a descriptive way to career patterns and the presence of children. Most of these first two sections are essentially updates of part of a previous IFS briefing note, published in 2016, which was the first output on the gender wage gap in this research programme and which set out some of the basic facts about the topic. In Section 3, we turn to our new estimates of the causal role of experience in determining the gender wage gap. We draw our conclusions in Section 4.
The analysis uses three large-scale UK data sets: the Labour Force Survey (LFS), the British Household Panel Survey (BHPS) and Understanding Society (USoc). Readers interested in the details of the data used, and the methods employed, should see the accompanying IFS working paper, which sets these out fully.


Labour Market, Labour Economics, Childbearing: Fertility, Wages And Earnings, and Life Course Analysis



Is referenced by: McGuinness, F. and Pyper, D. (2018) ‘The gender pay gap’, House of Commons Library Briefing Paper, No. 7068. London: House of Commons Library.

Related publications

  1. Mothers working part-time hit hard by gender pay gap, study shows

    Monica Costa Dias, Robert Joyce, and Francesca Parodi

  2. Part-time working hits women’s long-term pay growth

    Monica Costa Dias, Robert Joyce, and Francesca Parodi

  3. Mothers suffer big long-term pay penalty from part-time working

    Monica Costa Dias, Robert Joyce, and Francesca Parodi

  4. Mothers suffering 'pay penalty' at work, report suggests

    Monica Costa Dias, Robert Joyce, and Francesca Parodi


Research home

Research home


Latest findings, new research

Publications search

Search all research by subject and author


Researchers discuss their findings and what they mean for society


Background and context, methods and data, aims and outputs


Conferences, seminars and workshops

Survey methodology

Specialist research, practice and study

Taking the long view

ISER's annual report


Key research themes and areas of interest