The increasingly studied effects of working time reductions (WTR) on social, economic, and ecological sustainability depend on how these reductions are conceptualized in terms of implementation level, form, extent and accompanying wage compensation. Very little research on WTRs considers more than one sustainability dimension or explores different conceptualizations of WTRs. We thus seek in this article to differentiate the effects of diverse conceptualizations of WTR policies within and across all three sustainability dimensions by conducting a systematic review of longitudinal and (quasi-)experimental research on the ecological, social, and economic effects of WTRs. The studies we reviewed on social sustainability (n = 18) suggest that WTRs have generally well-substantiated positive effects on well-being, health, and work-family conflict. Regarding economic effects (n = 14), however, the findings are mixed: WTRs appear to have small, positive employment effects and unclear productivity effects, on one hand, as well as negative career-trajectory effects, on the other. The only study reviewed concerning ecological sustainability suggests that WTRs have a positive effect on the environment. Research on different conceptualizations of WTRs is scarce but suggests that WTRs might be most beneficial when implemented with a substantial reduction in working hours, on the national or organizational level, in the form of fewer rather than shorter working days, and accompanied by progressive wage compensation. Based on these findings, we also outline a research agenda to address the knowledge gaps in this important field of study.
