Prior research documents that providing relative performance information (RPI) motivates employees to increase effort; however, a potential downside of RPI is that it also motivates employees to distort their effort allocations between tasks such that it can be detrimental to overall firm performance. This study investigates via an experiment how the informativeness of RPI affects employees' effort allocations and performance in a multitask environment. We investigate the informativeness of two RPI design choices that are observed in practice: detail level and temporal aggregation. Regarding detail level, firms may provide each employee's performance ranking on tasks, which is less informative than providing the actual performance score of each employee. Regarding temporal aggregation, firms may provide RPI that is reset each period, which is less informative than RPI that is based on cumulative performance. We find RPI detail level and temporal aggregation interact to influence effort distortion. Specifically, we find that, compared to reset RPI, cumulative RPI leads to greater distortion of effort away from firm‐preferred allocations and that this effect is magnified when RPI provides actual performance scores rather than performance rankings. Finally, high levels of effort distortion hurt overall performance, thereby demonstrating the potentially detrimental effect of effort distortion on performance. Results of our study enhance our understanding of how firms can use their control over the design of RPI to enhance its usefulness in directing employees' effort in multitask environments by highlighting the role that informativeness of information can have on employee behavior.