Companies are giving employees AI tools to make them more productive, but the tools appear to be creating new problems for their managers.

More than half of senior leaders say they find it harder to evaluate employees’ work after adopting AI, according to a Nielsen survey of 1,700 directors and senior managers across seven countries, commissioned by work-management company Monday.com. The reason is that much of employees’ output now arrives polished in the manager’s inbox, making it hard to tell how much came from the employee and how much from AI. As a result, nearly half of managers say they spend more time reviewing and guiding their teams’ output than they used to.

That’s not to say managers are unhappy about AI. Quite the opposite, in fact: 94% of the managers polled said they were excited to improve work using AI, and many are confident they know where to use it to get the most value. Michal Miller Levi, head of market research and customer insights at Monday.com, compared the enthusiasm to the early days of the internet in the 2000s, saying people see a similar kind of “magic” to AI.