Relatively little, however, is known about how the length of the working day affects workers’ performance. From a theoretical point of view, two contrasting effects are possible. On the one hand, if part of the working time has to be used to prepare for work before one can actually become productive (e.g. exposing goods one wants to sell, or getting back to where one left in a complex cognitive task), then short working hours are not worth the trouble and longer working hours are better for performance. On the other hand, longer working hours can result in fatigue, which is likely to cause lower performance as the number of hours worked increase.
Although scholars have started to analyze the relation between working hours and worker performance already in the early 20th century, there is still not much conclusive evidence about how exactly and how much working hours affect performance. Existing studies have either relied on historical data, e.g. from munition workers during WW1 or from the Hawthorne experiments, or on data from the health sector, in which fatigue can result in human errors with crucial consequences.
Fatigue plays an important role
In a recent IZA Discussion Paper, Marion Collewet and Jan Sauermann use data on working hours and performance of a sample of call agents from a call center located in the Netherlands. Although call agents in this call center predominantly have part-time contracts, their job is demanding due to the constant inflow of calls generating constant pressure to perform. The authors find that agents have lower performance per hour on days on which they work longer hours. If one increases the length of a shift by 1 percent, the call agent’s output, measured by the total number of calls handled, increases by only 0.9 percent. This result suggests that fatigue plays an important role. Interestingly, the quality of the service provided seems to slightly increase with hours worked.
Since these results are found for workers who are employed in part-time contracts, fatigue effects might be stronger in other service jobs with longer average working hours.
Download the paper (IZA DP No. 10722):
Read also these IZA World of Labor articles on related topics:
- Employment effects of longer working hours
- The importance and challenges of measuring work hours
- Longer working hours lead to weight gain