Full-time hours, part-time work: questioning the sufficiency of working hours as a measure of employment status

ABSTRACT Although distinctions between full-time and part-time work are vital for understanding inequalities at work and home, consensus and critical reflection are lacking in how employment status should be defined. Full-time and part-time work are often represented as a binary split between those working under or over a specific number of hours. However, this paper, using exploratory mixed methods, evidences problems with assumptions based on working-hour thresholds and highlights the importance of workplace culture and household contexts. Using the UK Labour Force Survey we reveal ambiguities in the reporting of employment status for 12% of workers when comparing definitions based on number of working days, working hours and self-assessment. Ambiguities are particularly prevalent among working mothers with almost a third, who would be regarded as working full-time using hour-based measures, classified as ambiguous according to the measures used here. In-depth interviews with parents who self-classify as part-time workers, despite working over 35 hours a week, reveal mechanisms behind ambiguity within this group linked to organisational norms, previous working hours and divisions of household labour. The paper therefore argues workplace and household contexts are crucial to understanding employment status and recommends this should be taken into account in new multidimensional measures.


Introduction
Distinguishing between full-time and part-time work is a vital aspect of understanding work-life inequalities. Research regularly finds that part-time working is associated with greater precarity, workplace stigma, career penalties and lower pay (Blackwell, 2001;Chung, 2020;Manning & Petrongolo, 2008;Nightingale, 2018;Walsh, 2007). Employment status also has consequences in the home, with part-time workers found to make greater contributions to housework and childcare (Bünning, 2020;Schober, 2013). In many countries, such as the UK, it is common for women to move to part-time work when they have children and this has been credited as one of the key contributors to the 'stalled gender revolution' and the gender pay gap (Costa Dias et al., 2018;Nightingale, 2021). Estimates of who will suffer part-time penalties and how gender-unequal labour force participation is in a country, as well as the ability to distinguish between groups of part-time workers with different labour market positions, hinge on the choice of employment status definition. However, flexible working literatures point to limitations of existing measures (Chung & Tijdens, 2013;Figart & Golden, 2000;Mccomb et al., 2005) and, within the broader literature on employment, there is a lack of consensus and critical reflection on how we should classify someone as a full-time or part-time worker (Dixon et al., 2018;Walling, 2007).
Working-hour thresholds are typically used in research to determine full-time and parttime status, but raise technical and conceptual objections. There is no consistency on where these thresholds should fall and hours understood to be 'full-time' differ both between and within countries (Dixon et al., 2018;Thurman & Trah, 1990;Van Bastelaer et al., 1997;Walling, 2007). For example, in Singapore part-time work is regulated in labour law at less than 35 hours a week, in Brazil it is less than 30 hours and in the UK there is no legal threshold. The UK is used as a country of focus in this paper due to this ambiguity and the existence of large shares of workers doing short, standard, and long hours (Bielenski et al., 2002;Connolly et al., 2016;OECD, 2018). Hours-based measures have been criticised for their overly reductive measurement of complex and diverse lived experiences (Baffoe-Bonnie & Gyapong, 2018) and some argue measures should instead place a greater emphasis on self-assessment (Dixon et al., 2018). The present paper contributes to these debates by innovatively combining quantitative and qualitative analyses to give a direct indication of the validity of employment status measures in a UK context, revealing discrepancies between standard academic measures and the ways in which part-time and full-time work are distinguished in practice by employers, by workers and by family members.
Taking an inductive approach, the paper first discusses a quantitative study, which asks how prevalent ambiguity is in the UK populationby comparing measures of selfassessment, working hours and days workedand investigates who reports ambiguously and in what way. The findings indicate that 12% of all UK workers, and 23% of professional mothers, could be misclassified using standard hours-based measures. Building on these findings, the paper then analyses qualitative data from research with British parents in professional occupations to investigate what mechanisms underpin the high levels of ambiguity in this demographic. In this study, ambiguities were observed among four parents who worked in excess of 35 and even 40 hours a week, but self-classified as part-time. Reasons for these ambiguities in employment status centred around: comparisons with previous working hours and organisational working norms; employers' understandings and employment contracts; experiences of part-time penalties and stigma; number of days worked; and childcare divisions. Based on these findings, this paper argues that it is unclear whether those who are currently defined in the literature as full-time are perceived as such in practice. Recognition of ambiguity and re-examination of methods for distinguishing between parttime and full-time work are therefore recommended. Before setting out this empirical research, the paper first details how part-time and full-time work have been distinguished in the literature and the implications of these distinctions for knowledge about work-family experiences.

The implications of full-time and part-time definitions
At the most basic level, part-time workers are assumed to work shorter hours than fulltime workers, however broader assumptions are frequently made about the experiences of these two groups. Although laws in the UK prevent part-time workers from being treated differently to full-time workers, part-time work is assumed to be more precarious than full-time and is associated with lower wages, less responsibility and reduced opportunities for career progression (Blackwell, 2001;Manning & Petrongolo, 2008;Nightingale, 2018). In most cases, those classified as part-time workers will also receive benefits and allowances (e.g. annual leave) as a fraction of that offered to fulltime colleagues. Culturally, part-time working conflicts with 'ideal worker norms', which valorise presenteeism and prioritisation of work over other responsibilities (Acker, 1990;Blair-Loy, 2006;Williams, 2000). For these reasons, part-time stigmatisation and penalties are commonly reported (Chung, 2020;Walling, 2007) and are understood to be particularly prevalent in industries or occupations with long working-hour cultures and 'work devotion schemas' (Berdahl et al., 2018;Williams et al., 2013).
Within the work-family domain, employment status is regularly used to make inferences about the division of both paid and unpaid work (Ferragina, 2019;Zagel and Van Winkle, 2020). For example, 1.5 earner households are generally considered as representing a more specialised division of labour than dual full-time earners, because it is assumed that the part-time earner will have more time to invest in care responsibilities and housework during the week (Boeckmann et al., 2014;Iseke, 2014;Schober, 2013). Since part-time working is typically undertaken by women, employment status is also frequently used as an indicator of gender inequality in labour market positions within comparative studies (Ferragina, 2019;Zagel & Van Winkle, 2020). Definitions of employment status have further implications for understanding intersectional inequalities in working experiences. For example, there are class distinctions in women's experiences of part-time work due to contrasts between 'good' part-time jobs, typically undertaken on a temporary basis by middle-class professionals, and 'bad' part-time jobs in industries that are based on flexible and precarious working models, which are more reflective of working class experiences (Nicolaisen & Kavli, 2019;Tilly, 1996;Webber & Williams, 2008).
Given these far-reaching implications, it is crucial to ensure that assumptions about the realities and consequences of part-time/full-time employment status are valid. Yet, measures are often adopted uncritically and there has been limited analysis of how part-time and full-time work are defined (Dixon et al., 2018;Thurman & Trah, 1990;Van Bastelaer et al., 1997;Walling, 2007, notable exceptions include Baffoe-Bonnie & Gyapong, 2018. In the remainder of this section, we discuss three measures of employment status that previous research has attributed importance to: working hours, working days and self-assessment. We build on previous research regarding the validity of these measures and reflect on the way they have been used to proxy broader concepts in the work-family literature.

Working hours
The most common way of defining employment status is according to usual weekly working hours in paid employment falling above or below a specific threshold (Van Bastelaer et al., 1997). Hours-based definitions are used frequently in the academic literature, by international research organisations and in political contexts. For example, the OECD uses a threshold of 30 hours for full-time work, which is adopted in many studies including longitudinal analysis of UK household labour force data by Connolly et al. (2016), who find that the proportion of families where both parents work full-time has equalised with those in 1.5 earning households and see this as an indicator of movement towards gender equality.
However, a key issue with hours-based definitions is that there are no recognised standards about where cut-off points should fall (Walling, 2007). What may be considered part-time hours in one industry or occupation could be considered full-time in another, and changing thresholds can have a considerable effect on the reported incidence of part-time and full-time working (Hotchkiss, 1991). The observed rise in dual full-time earner couples in the UK noted above is driven by women in industries and occupations prone to long working-hour cultures (Connolly et al., 2016). This calls into question whether passing an hours-based threshold set at 30 or 35 hours can be associated with a reduction in part-time working among women or increasing gender equality, particularly if this does not correspond with contextual understandings of full-time work. Defining employment status based on working hours is further complicated by varying working-hour norms across countries that are not picked up by a binary measure (Van Bastelaer et al., 1997).

Self-assessment
As a result of the lack of consensus around working-hour thresholds, some, such as the Statistical Office of the European Union (Eurostat), use alternative measures of employment status based on working identity. Dixon et al. (2018, p. 4) propose that employment status should be conceptualised as 'a socially constructed category that varies across time, place, and individuals' and measures should therefore place a greater emphasis on selfassessment. In empirical research, this either involves asking respondents whether they self-identify as a part-timer or full-timer, or asking how their employer describes their job.
Yet, in practice, measures of working identity can be hard to differentiate from working hours due to survey prompts phrasing response options along the lines of: 'Full-time (30+ hours a week)' and 'Part-time (10-29 hours)'. The International Social Survey Program's module on work orientations (ISSP, 2017) even allows different hour-thresholds to be inserted in prompts across questionnaires: full-time is left undefined in the UK survey, identified as over 30 hours in the USA and over 37 hours in Belgium. Furthermore, validation checks on self-assessment measures can cause participants to be reclassified based on working hours if they fall outside predetermined extremes (Walling, 2007). In this way, surveys make assumptions that working hours 'trump' self-assessment after a certain point.
Conceptually, Walling (2007) points out that a limitation of identity-based definitions is that respondents could interpret part-time/full-time work according to many criteria (such as employer descriptions; contractual or usual hours; industry norms; and comparisons with others or previously worked hours). Indeed, qualitative research indicates that workplace context and gender roles within the family are important in self-perceptions of working status and identity (Young, 2018). Walling (2007, p. 38) concludes that 'differences in part-time employment rates between subgroups of the workforce could therefore simply reflect differences in the way that individuals in those subgroups interpret the concept of part-time work'. However, these diverse understandings of employment status could also be interpreted as a limitation of a working hours approach. Employer understandings and industry norms are likely to have a greater impact on lived experiences of part-time working than standardised thresholds.

Working days
Scheduling of work is an important dimension for lived experiences of employment status. Definitions that do not take into account how hours are scheduled could diverge substantially from those that do (Lawrence & Corwin, 2003;Lirio et al., 2008;Stone & Hernandez, 2013). Working hours could, for instance, be: predictable or unpredictable, constant or varying, condensed into a few long working days or spread out over multiple short days, all with major consequences for working identity (Jacobs & Gerson, 2004;Williams et al., 2013). In professional occupations with long working-hour cultures, compressed schedules such as 4.5-day weeks or 9-day fortnights have been associated with 'time deviance' and lower 'devotion' to work (Epstein et al., 2014;Wharton & Blair-Loy, 2002;). These schedules are generally negotiated arrangements that may prompt considerable resistance with management and are in conflict with assumptions that full-time workers are available five days a week (Lawrence & Corwin, 2003;Lirio et al., 2008;Stone & Hernandez, 2013).
Motivations to reduce working days are often linked to responsibilities outside the workplace such as providing mid-week childcare (Chung & Van Der Lippe, 2020;Fagan, 2001;Lambert et al., 2019;Walsh, 2007). Schedules of work are therefore associated with divisions of labour at home, as well as scheduling and availability of formal childcare and schooling (Ekinsmyth, 2011). While the number of working days alone do not give a firm indication of employment status, they can provide important context about different working schedules in a multidimensional model.

Permutations of working hours, days and self-assessment
In summary, although working hours are commonly used to classify employment status, the broad literature on work and family makes many assumptions about full-time/parttime work that extend beyond the number of hours worked. Whether measures of employment status reflect the diversity of real-world working experiences has implications for estimations of the prevalence and consequences of part-time and full-time working.
To understand how ambiguities between different classifications of employment status might arise, we move from single measures to multidimensional conceptualisations of individual working patterns and consider their interaction. Workers might be understood as part-time because they see themselves as such ('part-time identity'), because they spread their hours over less than a standard five-day working week ('part-time days') or because their working hours fall below a specified threshold ('part-time hours'). We combine these three indicators of employment status discussed above and investigate whether respondents report part-time status on all three, on none, or something in between. This results in the seven substantive categories shown in Table 1: unambiguous part-time (categories 1a and 1bthose who identify as part-time and work less than 30 hours 1 ); unambiguous full-time (category 7those working 30 or more hours, identifying as full-time and working 5 days a week) and five ambiguous categories (2 through 6), where the worker meets only some of the full-time or part-time assumptions and conventional hour-based definitions could lead to misinterpretation. As this is an exploratory study, this schema is not put forward as a theoretical model but simply as a way of mapping all possible employment status combinations based on three indicators.

Quantitative study
Given the potential implications of mismatches between different measures of employment status, two explorative research questions were studied using quantitative analysis of large-scale survey data. The first asked whether there are ambiguities in employment status based on self-assessment, hours and days and, if so, which demographics report ambiguously. The second research question asked what patterns of ambiguous reporting are associated with different demographics and aimed to provide insights into the way in which different measures were incongruous.

Data
Data from the fourth quarter of the 2018 UK Labour Force Survey (ONS, 2019) were used since this is one of the only representative UK datasets including questions measuring respondents' self-assessments of part-time/full-time status, working hours and working days.
Employment status based on working hours, was measured using a binary indicator where respondents who usually worked 30 hours or more per week in their main job (including paid and unpaid overtime) were considered as full-time. Usual working hours were chosen over working hours in the reference week, since respondents' identities are more likely to be tied to longer-term working patterns. The threshold of 30 hours follows OECD standards and is common in country comparative research (Walling, 2007). Self-assessment of employment status was based on a binary indicator measuring whether respondents self-defined as full-time workers or part-time workers. The survey question did not include any prompts with regard to hours, the item preceded other questions about working hours, and interviewers were specifically instructed not to provide guidance. However, identifying ambiguous classifications at the tails of the distribution is impossible due to LFS validation checks: respondents self-identifying as full-time must work at least 16 hours and those identifying as part-time may work no more than 40 hours (Walling, 2007). Any resulting measurement error would lead to an underestimation of the phenomenon and would not interfere with the validity of results.
Employment status based on working days was measured using a binary indicator coding employment status as full-time if respondents reported working five days or more in their main job. Respondents who worked condensed weeks -4.5 day weeks(n = 222) or 9-day fortnights (n = 126) -were not asked this question and were manually re-coded as working 4.5 days.
Finally, six socio-demographic indicators were created to estimate the prevalence of reporting ambiguities across different social groups. Dummy variables were introduced for sex, parental status, having completed higher education (degree or equivalent), white British versus other ethnicity, and status in employment (self-employed versus employees). Finally, occupation was measured in three groups: low-skilled (including elementary occupations, operators, assemblers, crafts and trades workers); mediumskilled (ref. including technicians, associate professionals, clerks, and skilled service employees); and high-skilled (managers and professionals). In addition to this, two controls were added to the multivariate models: a continuous variable measured age (centred at the analytical sample mean) and sector was measured using the one-digit NACE code (ref.: wholesale and retail).

Analytical strategy
Analyses were restricted to the 38,881 respondents in dependent-or self-employment in the reference week, who had valid observations on all variables. 149 respondents who reported combinations of working hours and days that were either impossible or improbable (defined as working over 18 hours in a single day or working more days than hours 2 ) were excluded from the sample. Respondents reporting they worked multiple jobs in the reference week (<4% of the sample) were included because the LFS items measuring working days, hours and self-assessment were specific to the main job. Analyses did not lead to different conclusions based on the inclusion or exclusion of these groups. This resulted in an analytical sample of 29,504 individuals.
We used the seven-category schema presented in Table 1 to assess reporting ambiguities in this sample. The employment status categories were cross-tabulated with each of the six socio-demographic indicators using the weighted sample of the UK LFS to estimate the share of workers in the ambiguous versus unambiguous categories, as well as across the five ambiguous categories (Figure 1; Table 3). The  intersection effects of gender, parental status and occupational class on reporting ambiguously were then tested using a binomial logistic regression with a three-way interaction term (Table 2). To aid understanding, the marginal effects of parenthood by gender and class are displayed graphically in Figure 2.
To measure how respondents report ambiguously, a multinomial logistic regression measured selection into each of the five ambiguous categories for the six demographic groups. A three-way interaction measured the differential effects of parenthood across gender and occupational class. All results are presented in Table 4 using average marginal effects (AME), which should be interpreted as the percentage point increase in the absolute probability of being classified into an outcome category compared to all other outcomes rather than to one base outcome. AMEs are easier to understand than logistic coefficients and effect sizes are comparable across models (Breen et al., 2018). All results should be considered descriptive.
Finally, several robustness checks were performed to test the sensitivity of the findings to alternative operationalisations: the analyses were repeated using different thresholds for defining part-time work (less than 35 hours instead of 30 and 4 days or less instead of 4.5). Another test classified respondents according to their usual working hours excluding overtime. While these alternative measures inevitably affect the distribution, none of these tests removed the reporting ambiguities and the size of the ambiguous group remains relatively stable ( Table 2 in Online Material).

Who reports ambiguously?
Results indicated that 88% of UK workers reported their employment status in an unambiguous manner while 12% had an ambiguous employment status. Roughly two thirds of the respondents (66.5%) fell into the unambiguous full-time category and just under 22% were categorised as unambiguous part-time (Table 3). Ambiguities in reporting were not  limited to one specific demographic. Figure 1 shows the share of workers who are classified into one of the five ambiguous categories across the demographic groups.
Most notably, the proportion of men who were classified as ambiguous (9%) was much smaller than that of women (15%), suggesting that ambiguities in employment status are a gendered phenomenon. This appears to be the case especially for parents: 17% of mothers fell into the ambiguous categories compared to 13% of women without children, while the proportion of fathers in an ambiguous category was nearly equal to that for men without children (9%). A larger share of workers in low-skilled occupations fell into one of the ambiguous categories (13%) than in medium-skilled or professional occupations (both 11%).
Multivariate results suggest that gender, parenthood status and occupational class intersect in relation to ambiguous employment status (Figure 2; Table 2). Results show that the effect of being a parent on ambiguous employment status is significant for women, but not for men. Mothers in low-skilled occupations were not more likely to report ambiguously than childless women, however the probability of reporting ambiguously was 2.8 percentage points higher for mothers in medium-skilled occupations and 8.8 percentage points higher for mothers in professional occupations compared to their childless peers. Descriptive statistics in Table 3 show that the employment status of 23% of mothers in professional occupations was classified as ambiguous. What kind of ambiguous combinations are found?
The vast majority of those categorised as ambiguous would be classified as full-time according to hours-only definitions of employment status, which suggests that survey data potentially over-estimate the number of full-time workers. As Table 3 shows, these include people who worked full-time hours (≥30 hours ) but reported working parttime days (category 5, 6.8%), self-assessed as part-time (category 4, 1.55%) or both (category 2, 2.18%). The remainder of the ambiguous respondents would be considered part-time by hours-only definitions: they self-assessed as full-time workers despite working fewer than 30 hours per week over five weekly work days (category 6, 0.8%) or over fewer days (category 3, 0.5%). Gender differences were found in the reporting of working in excess of 30 hours over fewer than five days and identifying as part-time workers: 3.6% of women compared to 1% of men (category 2). Larger shares of women than men also self-assessed as part-time despite working full-time hours and days (2% vs. 1%, category 4) and reported part-time hours in combination with full-time days and identities (1% vs. 0.5%, category 5). Differences between fathers and childless men were small. Larger differences were found between mothers and childless women, especially at the intersection with occupational class, as described in the multivariate results ( Figure 2; Table  2).
We explored whether the intersection of gender, parental status and occupational class significantly affects the probability of being classified into specific ambiguous categories by running a multinomial logistic regression (Table 4, marginal effects presented). The models confirm previous findings that childless women in medium-skilled and professional occupations had a lower absolute probability of reporting employment status unambiguously than childless men, but also show that the probability was 3% points higher for childless women in low-skilled occupations (.031, p<.01) than for childless men. Hardly any effects associated with being a parent were found for men. No effects of parenthood on women in low-skilled occupations were found either, except for a marginally significant higher probability of self-assessing as part-time and working over 30 hours in fewer than five days (.012, p<.1).
Parenthood was associated with more and larger effects for women in medium and professional occupations. Both mothers in medium-skilled (.022, p<.000) and in professional (.056, p<.000) occupations had higher probabilities of reporting part-time days and identities in combination with full-time hours. Mothers in medium-skilled occupations furthermore had 1 percentage point lower probabilities of identifying as full-time workers and working full-time hours in combination with part-time days (−.013, p<.05) and a 2 percentage points higher probability of self-assessing as parttime while working full-time hours and days (.017, p<.000). Mothers in professional occupations had a 3.5 percentage point higher probability than non-parents of identifying as full-time workers and working full-time hours in under five days (.035, p<.000).
Finally, although there was no evidence that self-employed workers, degree-holders and white workers were more likely to report ambiguously in the multivariate models (compared to employees, non-degree holders and non-white workers respectively), these demographics were associated with significantly different probabilities of selecting into particular ambiguous categories. Most notably, self-employed workers had a 2.3 percentage point lower probability than employees of working under five days while self-assessing as full-time and working over 30 hours (−.023, p<.000).
The analyses thus suggest that socio-demographic characteristics are associated with differing probabilities of ambiguous employment status, as well as specific patterns in the reporting of employment status. For women, motherhood is associated with higher probabilities of identifying as part-time while working full-time hours, full-time days, or both. Ambiguities were particularly high among mothers in professional occupations, followed by mothers in medium-skilled occupations.

Qualitative study
Since mothers in professional occupations were identified as a group with elevated levels of ambiguity in employment status, data from an existing qualitative study with this demographic was analysed to explore the mechanisms behind ambiguity. Although this small-scale study makes no claims to generalisability, the use of in-depth interviews provides an understanding of how people within this demographic who report ambiguously define their employment status and on what basis, which is not possible in largescale representative data.

Methods
The qualitative data come from a UK study, conducted by the first author, investigating how couples negotiate the division of paid work and childcare at the transition to parenthood. A short online recruitment survey was distributed via alumni departments at two UK universities and received 117 responses. Using questions on own and partner's working-hour bands from the survey, 17 co-habiting, heterosexual couples with preschool children were selected for interview to represent a variety of household working arrangements. The average age of interview participants was 36.9 years and around three quarters identified as White British. Three participants identified as White Irish, one as Bangladeshi and four as Indian or British Indian. The use of alumni departments meant all participants were educated to at least degree level. As a result, most were in highly skilled, professional occupations, however there was considerable variation in type of profession and location within the UK.
Semi-structured interviews were conducted in 2017 with each partner separately, lasted 42 minutes on average and took place over the telephone. Questions addressed how participants shared the responsibilities of childcare and paid work with their partner, and how decisions had been made regarding these divisions. For the purposes of this paper, transcripts of interviews were thematically analysed to explore the mechanisms behind ambiguous employment status.

Findings
Of note in this study were four parents who reported working well in excess of standard hour-based thresholds for full-time work, but who described themselves as part-time workers in the qualitative interviews. Two of these parents with 'ambiguous' employment status were in the same couple (Couple C) and the other two had partners with 'unambiguous' full-time status (Couples A and B).
As seen in Table 5, the women in Couples A and B described themselves as parttimers, despite working similar or even longer hours than their husbands who identified as full-time. The mother in Couple B worked such long hours that, if she had selfclassified as part-time in the UK LFS, validation checks would have automatically reclassified her as full-time. In Couple C, the husband and wife both described themselves as part-time, despite both working over 35 hours a week. They worked for the same employer and had both requested a move to what they termed '80% contracts' over four days when their daughter was born. All three of these couples would be classified as being in dual full-time earner households according to standard working-hour thresholds of 30 or 35 hours. However, based on their own definitions and number of days worked, two could be classified as 'standard' 1.5 earner households and one as dual part-time.
Why did these parents, whose working hours would categorise them as full-time according to most measures, self-classify as part-time workers? Absolute working hours did not feature often in participants' descriptions of their working patterns and some had to calculate how many hours they worked, indicating that this was not a common point of reference. Instead, reflecting Walling's (2007) and Young's (2018) assumptions about drivers of self-assessment, hours relative to previous working patterns and to those of colleagues or organisational norms appeared important. All four parents with 'ambiguous' employment status described themselves as having been in full-time work with the same employer before they had their first child and said they had subsequently moved to part-time. All four were also professionals with highly responsible roles in sectors that typically have long working hours: law, medicine, and scientific research (Table 3). Due to full-time working expectations being in excess of 40 hours a week in their organisations, they were still well above standard hours-based definitions of fulltime work after reducing their working hours. This indicates that ambiguity in employment status among professionals is linked to the particular working cultures of the industries in which they are typically employed. The literature points to part-time work being more stigmatised in these sectors (Berdahl et al., 2018;Williams et al., 2013). However, these findings suggest that large-scale analyses could underestimate the prevalence of part-time working in professional sectors if standard working-hour thresholds are adopted. It is notable that all four of these parents described negotiating part-time contracts with their employers, as illustrated in the following extract from the father in Couple C: I spoke to [a senior member of staff] who needs to support the application if you're going part-time. We also have a part-time advisor […] and she had a lot of advice about the practicalities of itmoney, training, what it's like to be 80%, what it's like to be 60%, what it's like to be 50%, who you need to get in touch with.
This indicates that ambiguity is not restricted to individual understandings, but also driven by workplace classifications. As these parents were contractually understood as fractional part-time staff, this is likely to have contributed to self-assessment through consequences for entitlements, such as annual leave, and broader experiences in the workplace.
Like many in part-time work, these parents appeared to face stigma and career penalties when they reduced their working hours (Blackwell, 2001;Chung, 2020;Manning & Petrongolo, 2008;Walsh, 2007). For instance, the lawyer in Couple B, who had been working 65-80 hours a week before children and was now working in excess of 40 hours a week over 4 days, described moving off a trajectory to partnership when she transferred to a 'part-time' position following maternity leave: "when you get to that partnership prospect, the idea that you can do that flexibly is not there at that level". The scientist in Couple A also implied she had experienced some stigma associated with her 'part-time' status, describing managers who "frowned on" flexible working and expected her to "be more visible".
Another important reference point in descriptions of employment status was days worked. All four parents moved from working five days a week to four when they reduced their working hours. When looking at comparisons with spouses, relative number of days worked appeared more important in understandings of employment status than relative working hours and this seemed to be closely linked to divisions of childcare responsibilities. Despite working long hours on other days, 'part-time' status provided 'protected' time for all four 'ambiguous' parents to dedicate one weekday to looking after their child. In Couples A and B, this meant they did more mid-week childcare than their 'full-time' working spouse who was employed five-days a week, as seen in this quote from the mother in Couple A: I wanted to try and have the best of both worlds: to have some time with her just myself and then the weekend as a family.
[…] I think [my husband] would love to [work part-time too] and he takes the odd day off to spend with her and I know that he feels that he misses out. You know, sometimes he only sees her for a very short amount of time on a working day.
These interpretations of employment status based on days in work and days spent on childcare provide some explanation for the intersectional effects of occupation with parenthood and gender observed in the quantitative analysis.
In summary, ambiguity was derived from the resemblance between the lived experiences of these four 'full-time hours' parents and broader assumptions about part-time working, which is reflected in self-assessments. Despite working full-time according to standard hours-based definitions, the three women were, in practice, following the norm of mothers reducing their working hours after maternity leave (ONS, 2017) to take on childcare responsibilities (Schober, 2013). This had negative consequences in the workplace, including career penalties and stigma. Gendered disparities in earnings and unpaid work also increased in the home, since most men's working patterns had not changed in the same way following the transition to parenthood. Interpreting these four 'ambiguous' parents as full-time workers would appear to be problematic and, if, as our quantitative results suggest, their experiences mirror broader trends, this could have important implications for understanding inequalities at work and home. The presence of one 'ambiguous' father suggests that more men could also be understood as part-time workers than current definitions indicate, particularly since industries with long working hours tend to be male-dominated (Cha, 2013).

Conclusions
This paper has responded to calls for more critical reflection on distinctions between parttime and full-time working (Dixon et al., 2018) by considering the validity of hours-based measures of employment status. Although the weaknesses of working-hour measures have been identified in flexible working literatures (Chung & Tijdens, 2013;Figart & Golden, 2000;Mccomb et al., 2005), distinctions between full-time and part-time working are often taken for granted in the broader literature on employment and, in some cases, methods of classification are not even provided. The contribution of this mixed-methods paper has been to quantify the extent of ambiguity in employment status in the UK and to indicate the problems that can arise when assumptions about working patterns are derived from standard hours-based measures. It has also identified groups where ambiguity is most prevalent and has explored how and why these groups present with ambiguous employment status.
Using the UK LFS, quantitative analyses reveal that 12% of British workers are classified as ambiguous when definitions of employment status based on respondents' number of working days, working hours and self-assessment are compared. In the UK alone, this represents more than 2.5 million people whose employment status could be misinterpreted. Most of these ambiguous respondents are classified as full-time workers using hours-only measures, which implies that studies using working-hour thresholds to measure employment status may commonly underestimate the prevalence of part-time work and miscalculate repercussions. Analysis of socio-demographic characteristics indicates that it is especially problematic to apply a simple hour-based measure to mothers, since ambiguity is elevated among this group. This is particularly the case for mothers in professional occupationsalmost a quarter are classified as ambiguous according to combined measures. Furthermore, in-depth interviews indicate that professional mothers report part-time penalties despite working hours that would be categorised as full-time in large-scale surveys. These findings are therefore especially pertinent for the work-family literature. For example, there could be implications for claims that dual full-time earning and moves towards a 'gender egalitarian equilibrium' are on the rise among UK parents (Connolly et al., 2016).
Our analysis of qualitative data from an existing study with parents in professional occupations indicates some mechanisms for ambiguity among this group. Despite working over 35 or even 40 hours a week, three mothers and one father in this study self-classified as part-time and were understood as such by their employers and partners. Their experiences reflected many of the assumptions made about part-time working parents: reduced earnings, inferior career prospects, workplace stigma and responsibility for a larger share of mid-week childcare. Classifying these parents as full-time following common hours-based thresholds therefore appears problematic. As well as experiences of part-time penalties and stigma, number of days worked, organisational norms and comparisons with previous working hours appeared pivotal in understandings of employment status.
It is important to note that this paper is unable to provide any indication about causality, since these analyses are explorative, and the statistics are descriptive. The qualitative study was non-representative and limited to 34 heterosexual parents in cohabiting couples from a privileged, professional demographic. The findings are therefore not generalisable, although quantitative analyses of the UK LFS (a large-scale representative dataset) have allowed us to report on the prevalence of ambiguous employment statuses with confidence. Nonetheless, both studies are limited to a UK context. Since the findings support the notion of socially constructed and contextually understood definitions of employment status, the phenomenon of ambiguity is likely to vary cross-nationally and be more prevalent in countries with long working-hour cultures and traditional gender norms around men's and women's roles. Future research should include countries with different practices and policies towards working time and mid-week childcare.
Since distinctions between part-time and full-time employment are frequently used across the social sciences to make assumptions about practices at home in the workplace, mismatches between definitions and lived experiences can have important consequences for the validity of research conclusions. The paper therefore recommends a reconsideration of distinctions between part-time/full-time status based on working-hour thresholds. Although self-assessment appeared to be a better indicator of lived experiences than working hours in the qualitative study, we do not advocate replacing one measure with the other due to the limitations of self-assessment for comparative research (Walling, 2007). Instead, we recommend that future research build on the approach adopted here to develop a multidimensional measurement of employment status and call for the inclusion of more items for employment status in large-scale survey infrastructures, ensuring that these are distinct (for example, avoiding working hours prompts in self-assessment questions).
Future research should also consider the mechanisms behind understandings of employment status from employers' perspectives, since this appeared to be important in qualitative participants' self-assessments. To ensure multidimensional measures reflect the diversity of lived experiences, qualitative research must additionally investigate how other groupssuch as self-employed or gig workers and workers in lower-skilled occupationsunderstand full-time/part-time distinctions. In lower-skilled occupations, where workers generally experience less autonomy or flexibility, we might expect ambiguities to be more strongly driven by irregular work-scheduling practices, such as on-call hours and rotating shifts, than employee requests for reduced or condensed hours. For this reason, we suggest that the degree of stability in self-identified employment status will be of particular interest when studying workers with irregular (shift) work schedules and high variability in the number of hours and days worked, including self-employed and (on-call) shift workers.
Given that our data pre-dates the COVID-19 pandemic, further investigation is additionally required to consider whether changes to working and caring practices have had consequences for employment status distinctions and levels of ambiguity. For example, if more flexible and home-based models persist, the role of working days in understandings of employment status could become more complex, while reported increases in fathers' childcare provision (Andrew et al., 2020;Yerkes et al., 2020) could lead to greater levels of ambiguity for men.
In the immediate term, working within the limitations of current measures and available data, the findings presented here indicate that it is important for researchers to acknowledge the possibility for ambiguity in employment status and the limitations of existing measures. Results should also be interpreted with these limitations in mind and caution placed on the assumptions and conclusions that can be made from the measures used. Quantifying ambiguity, as here, could help contextualise the validity of conclusions.
Notes 1. A differentiation is not made here for number of working days, since both working fewer than five days and working five short days could meet all assumptions about part-time work 2. Our consistency checks show that most respondents who report impossible or improbable combinations of usual working hours and days are self-employed workers. We attribute this reporting to frequently changing work patterns and suspect respondents estimated average usual working hours and days independently.