Associations between employee and manager gender: impacts on gender-specific risk of acute occupational injury in metal manufacturing

The demographics of the US workforce continue to change with respect to women [1]. Women’s labor force participation is projected to increase 7.4% between 2010–2020 compared to 6.3% for men in the same period [2]. The changing composition of women in the workforce is reflected in management where there has also been a marked increase. The percent of women in management in the private sector increased from 32.7% in 1998 to 36.9% in 2011 [3]. Our own research setting, the fabricated metal product manufacturing industry, has one of the lowest percentages of female managers; in 2012 16.5% of industrial production managers were female [4].

As the number of women in managerial roles increases, particularly in the manufacturing sector, understanding the consequences on worker outcomes becomes increasingly necessary. Previous studies suggest that managers and management are a major determinant of workplace safety culture [5]; however, prior research focuses largely on men and does not consider the impact of manager gender. Of particular interest is worker injury because women employees experience a higher rate of injury for comparable job titles in many industries [6–10]. In a cohort of heavy manufacturing employees, women were found to have a 37% increase in risk compared to men [6]; female postal workers in their first year of employment had nearly double the risk of male workers (RR 1.93) [7]. In semiconductor manufacturing, women had a higher incidence rate for injury and illness than men [8]. Among utility workers, the rate ratio for injury for females compared to males was 1.5 [9] with the effect persisting in analyses of more severe injuries.

There have been several hypothesized reasons for the higher rate of injury amongst women including 1) a lack of tailoring of workplaces for female ergonomics and ill-fitting safety equipment [11] 2) a lack of formal job training and/or informal training through childhood activities and past jobs compared to men [9], 3) differential injury reporting, where men and women report injuries differently or experience injuries differently, particularly mild injuries [7, 12], 4) social isolation (whereby women feel that they cannot ask for help when necessary), and 5) work-family conflict [13].

While the first two pathways, lack of tailoring of equipment or childhood experience, are unlikely to be related to the gender of an employee’s manager, there could be pathways whereby manager gender mediates women’s injuries through each of the last three mechanisms or through some combination of these. First, women may appear to have more injuries because of differences in reporting; reporting may potentially differ by manager gender or by whether employee and manager gender are concordant or discordant. Second, if a female employee is discordant with her colleagues and manager, she may be isolated and more at risk of injury. Third, it is possible that female employees have different psychosocial strains such as family responsibilities and responsibility for child care than male employees. Consequently the differences in management style, particularly styles related to gender norms, might help buffer against these psychosocial strains. Overall, it is ex ante ambiguous what effects an employee’s manager’s gender might have on the increased risk of injury experienced by female workers.

This study is an exploratory analysis of the effect of manager gender. In particular, we seek to explore whether an employee’s manager’s gender moderates the effect of employee gender with regards to risk of acute injury.

Figures 1 and 2 present percentages of male and female employees in each category of manager type by year over the study period and percentages of female employees by year over the study period respectively. During this period, the percentage of employees who had both female and male managers doubled, with corresponding drops in employees with female managers only and male managers only. Very few male employees were in departments for which all managers were female; this percentage stayed fairly constant at about 6% for most of the study period.

The 99 departments included had an average count of 51.7 employees (SD 61.2, median 29). Of these, 30 (30.3%) were considered high physical demand based on job titles within the department.

Figure 3 presents Kaplan-Meier survival estimates by manager gender category for female and male employees separately. The descriptive plots show that by 3 years (36 months) over 25% of both male and female employees experience an injury, but there does not seem to be a marked difference by manager gender. In Table 3 these relationships are examined in a multivariate manner using Cox proportional hazards models. In all three models, the Wald p-value for the interaction between employee gender and manager gender category was not significant and the interaction was excluded from models in Table 3. Results from the interaction models are included in the Additional file 1: Table S1. In the adjusted model including a frailty term at the department level (Model 3), female gender was associated with a HR of 1.21 (CI 1.06 – 1.39) compared to male gender for injury risk. Manager gender category was not significantly associated with injury risk (p = 0.093) when comparing both female and male managers and only female managers to only male managers.

Our analysis of light manufacturing employees at six facilities of a major US aluminum company does not suggest that the increased hazard of acute injury associated with female gender is modified by the employee’s manager’s gender.

The inability to demonstrate any benefit in terms of the gender disparity in injury risk consequent to a major ramp-up in the gender mix of supervisors sheds some light on the cause or causes of the disparity: Either gender-match is insufficient to buffer the social causes such as isolation, management of personal family conflict or differential reporting, or those causes are less salient than ergonomic differences between men and women, or differences in their overall training. While there are undoubtedly numerous reasons to expand the numbers of women in these traditional male supervisory roles, reduction of female injury risk does not appear to be a strong one.

Our analysis found that female employees had a 20% increased risk of injury compared to male employees. This is similar to the finding by Taiwo et al. in heavy manufacturing workers at aluminum smelters where female employees had an increased risk of 37% compared to male employees [6]. Similar results have been found in other settings. Kelsh et al. found that after adjusting for occupation, job experience and age, female electric utility workers had a higher rate of injury compared to males [9]. Similarly, higher incidence of injury among females was observed in a cohort of semiconductor manufacturing workers by McCurdy et al. [8]. Buchanan et al. found that female hotel employees were injured more frequently than male employees; the majority of housekeepers, who experience high physical demand, are women [20].

Surprisingly, being in a high demand department was consistently associated with a reduction in hazard of acute injury in this subset of plants. A possible explanation for this is the healthy worker effect, i.e. those who are injury-prone are selected out of high demand jobs. Further, departments designated as high demand contained a much higher percentage of male workers than non-high demand departments and employees in these departments had significantly longer tenure in their department. “High demand department” may be reflective of factors we were unable to capture, such as tenure at the company, skill level, experience with a particular task, and dynamic selection into and attrition out of high departments based on previous injury experience and/or safety culture [21, 22].

Secondary analyses using presence or absence of a female manager in the department support our primary result and suggest that the increased risk for female employees compared to male employees does not differ for departments with and without any female managers.

Results from outcomes restricted to first aid-only injuries and reportable injuries only did not differ from the main analysis for the research question exploring employee and manager gender concordance; however, reportable injuries make up a small fraction of injuries in the light manufacturing facilities we studied therefore we cannot be sure whether our results reflect a lack of power or a true null relationship between manager and employee gender. Of note, while a higher proportion of females experienced a first aid injury compared to males, the relationship is opposite for reportable injuries with a higher proportion of males experiencing a reportable injury compared to females. This is likely to do with differing potential for serious injury based on higher demand jobs, which are mostly done by men.

Further, we find some evidence that for first-aid injuries, both men and women employees have a higher risk of injuries when in a department led by female managers only compared to those in departments led by male managers only. This may be due to reporting of injuries by employees or by managers, or be due to the increase in female managers occurring during the study period – freshman managers have less experience in their department and may be more likely to report first-aid injuries than experienced managers.

A sensitivity analysis that used the previous year’s manager gender category was not different from the main analysis, suggesting that the effect of employees changing managers or departments in response to an injury is minimal. Sensitivity analyses that restricted analysis to employees starting in departments after Jan. 1, 2004, after the percentages of employees in each category of manager gender had stabilized, suggest that the effect of the change in manager demographics from 2002–2004 was minimal.

Strengths of this study include use of a cohort of manufacturing employees with a large number of female employees and female managers. Data, including injury and employment outcomes, were obtained from human resources records and an injury management database and not from self-report. Further, the real-time injury management database allowed us to examine first aid (non-reportable) injury as an outcome; this sector experiences few reportable injuries in proportion to total injury and this further allowed us to explore the issue of differential reporting.

This study does have important limitations. First, we were unable to distinguish floor managers from senior management when identifying managers. However, it has been suggested that both floor managers and senior management are very important to safety culture [5]. Another limitation is that men and women with the same job title may perform very different tasks [11], and that women are more likely than men to perform tasks involving repetitive motion and standing for extended periods [23]. Unmeasured confounders, such as work culture, that are associated with manager gender and injury as well as employment outcomes exist.

Given that only 17% of the employees were in departments with a discordant manager type (only female managers for a male employee and only male managers for a female employee), lack of power may have affected our ability to find a significant interaction between manager and employee gender. However, 13% of injuries were to discordant employees. We did not control for the number of hours worked, or overtime hours, and do not incorporate data on injuries after the first. Further, individuals may self-select into departments based on the gender of their manager, a factor we are unable to capture; however, this is unlikely to be the case in a period of rapidly changing manager composition. Perhaps most important of all, our dataset derives from a single industry and single safety-conscious employer, and hence is not necessarily representative of injury risks or their causes more generally.

As our analysis was exploratory in nature, these results can be used to inform future analyses of effect modification of risk of injury for men and women by their manager’s gender as well as future analyses exploring pathways for the increased risk of occupational injury for females compared to males. As the percentage of women in management increases, especially in previously male-dominated industries, it is important to consider the impact of manager gender on injury and employment outcomes. In this cohort of light manufacturing workers, manager gender does not appear to modify the increased risk of acute injury experienced by female employees overall.