Considerable variability has been observed in the number of working hours, both among and within countries. Previous evidence suggests a correlation between prolonged working hours and adverse health consequences1). While many countries have implemented legal restrictions on working hours to safeguard the well-being of workers, the prevalence of long working hours remains widespread2).
The global phenomenon of interest in reducing working hours has been documented for over 150 yr, beginning in the 18th century, and coinciding with the onset of the Industrial Revolution3). Meanwhile, workers came to realise that there was a lack of proportionality between working hours and productivity, prompting their insistence on the provision of sufficient rest periods and appropriate working hours. In this context, working time has been a significant issue for the International Labour Organization (ILO) since its foundation4). Establishing limits on daily and weekly working hours was the subject of the very first ILO Convention, the Hours of Work (Industry) Convention of 1919 (No. 1). In 1926, Henry Ford implemented a 40-h workweek, a decision that gained significant recognition5). Ford’s empirical investigations provided compelling evidence that reducing the workday from ten hours to eight hours, as well as the workweek from six days to five days, resulted in a notable enhancement in overall worker productivity and a reduction in production expenses4). Ford held a positive view of the societal advantages associated with a reduced workweek, emphasizing the notion that an extended period for engaging in consumption activities would be beneficial for all individuals. The basic premise of his reasoning was based on the notion that a decrease in shift duration would result in an increase in productivity. The average number of working hours in the United States significantly declined following the introduction of the 40-h workweek in 1936. Subsequently, other industrialized nations progressively followed this practice as a standard, starting in the 1970s3). Further, many industrialized nations have maintained consistent working hours for prolonged periods and are exploring ways to enhance productivity while reducing labour supply4).
Therefore, understanding the impact of working hours on labour productivity has emerged as a crucial topic for understanding labour demand and holds significant implications for regulating working hours and managing firms6). These issues are receiving great attention in efforts to address both the anticipated decline in the labour force, largely due to population ageing, and the desire to enhance domestic demand by increasing households’ purchasing power7).
For this, one important question is how to measure productivity. A relationship between output and inputs is the general definition of productivity. However, it is challenging to estimate productivity at the individual level, given that the nature of the work, the industry, and other contextual factors must be taken into account when measuring labour productivity. Additionally, to get a whole picture of productivity, qualitative factors like skill development, creativity, and employee satisfaction should be combined with quantitative data. When discussing productivity related with working hours, it is highly important to distinguish per-hour productivity from per-capita (per-worker) one. Even if overwork reduces per-hour productivity, increases in per-capita productivity are possible. Therefore, when considering a company’s profit, per-capita productivity is typically the main focus, while per-hour productivity is considered from the perspective of the workers’ performance. Similarly, it could be critical to differentiate between subjective (self-assessed) and objective productivity measurements. While research in occupational health and psychology use the subjective productivity measure, those in economics primarily prefer the objective productivity measure based on financial information of firms.
Overall, the growing diversity in the structure of working hours within organisations raises questions about its influence on firm productivity and performance. Employers strive to optimise employee productivity to generate high-quality products at minimal cost. The decisions made by employers regarding working hours involve a trade-off wherein a reduction in working hours has the potential to enhance labour productivity, but concurrently may result in an increase in the average labour cost due to hiring more workers8). Enhancing our understanding of firms’ or employers’ motivations to decrease or increase working hours may contribute to the development of more effective policies. Nevertheless, there are concerns that there is a lack of sufficient evidence regarding the potential decrease in per-capita productivity associated with shorter working hours. In addition, several economists contend that a reduction in working hours may not result in a substantial gain in workers’ per-hour productivity, but rather lead to an increase in labour expenses7). Along these lines, the effect of extended working hours on overall labour productivity has been a hotly debated issue among policymakers and economists.
Working hours have been investigated as one of the predictive factors of labour productivity mainly in terms of economics or human resources management. The literature is vast and nuanced, but most studies have concluded that there is an inverted U-shaped relationship between workload and performance9), and that overwork has a negative impact on labour productivity in both individual- and firm-level data, regardless of types of measurement for the productivity2, 4,5,6,7,8, 10,11,12). Moreover, a large number of recent studies have gathered empirical evidence that supports the idea that implementing a reduction in working hours while maintaining wage levels can be an efficacious workplace intervention for enhancing employees’well-being and fostering an increase in self-rated productivity13).
The most common factors affecting productivity during overtime are physical and mental fatigue11). Workers experience a certain level of physical and mental exhaustion as a result of the extended duration of their work shifts. Consequently, prolonged overtime is likely to lead to a rise in both absenteeism and presenteeism. Analysis of 4,197 Korean workers showed that working 52 h/week or longer is associated with a 5.1% point and 6.6% point higher health-related productivity loss due to absenteeism and presenteeism, respectively, compared to working 40 h/week, for both male and female workers10). Similarly, an analysis of broad, U.K. worker‐establishment matched panel data from 2004 to 2011 showed that long working hours are positively related to health‐related absenteeism14). Additional consequences of working overtime include heightened rates of injuries and accidents, diminished levels of supervision and efficacy, as well as an elevated likelihood of errors, which are especially significant when related to a lack of sleep5, 11).
What does all of this mean? Based on the research reviewed here, it comes down to worker’s health. At around 40 h per five-day workweek, workers seem to be able to maintain productivity fairly well, but when individuals exceed this threshold and engage in longer work hours, their job performance gradually weakens because of increased fatigue and underprivileged health conditions. Firms are faced with the task of making important decisions on both the allocation of working hours and the recruitment of employees. When increasing working hour, firm should incur an extra cost for the overtime pay and a decline in per-hour productivity. On the other hand, when increasing employment, firm should incur fixed costs (for example, hiring, firing, and training costs) but could gain an increase in per-hour productivity due to each worker’s decrease in working hours. A profit-maximizing firm will decide this by comparing the productivity and cost of both workers and hours. Increasing working hours is not the only option. Rather, as the literature repeatedly shows, it might be one of the very worst choices that is expected to fail in the long run. This is the fundamental rationale behind why most industries in developed countries gave up overtime practices over a hundred years ago. From this perspective, it is imperative for practitioners and policymakers to possess a comprehensive understanding of the outcomes of previous studies on this topic.
For making more practical decisions based on solid evidence, further research should be performed to validate previous findings. Several studies have been carried out using a variety of methodologies11, 13) but it is important to note that they have certain limitations. Many of them are outdated, based on small sample sizes, and largely derived from questionable or unknown sources. Moreover, studies from an occupational medicine perspective are still lacking. Future research should consider what characteristics need to be taken into account when workers want to quantify the effect of working hours on labour productivity in terms of personal preferences and health within the context of human capital.
Funding
This research is supported by National Research Foundation of Korea (NRF-2022R1F1A1066498).
Conflict of Interest
The author declares that there is no conflict of interests.
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