The usefulness of employee performance reviews depends on whom you ask.

A new survey by staffing company Accountemps found that 94 percent of CFOs said that formal evaluations of employees are either somewhat or very effective in helping employees improve their performance. On the other hand, the employees who are being evaluated do not necessarily agree with their bosses on that point. Nearly one in three workers, 31 percent, called performance reviews either somewhat or very ineffective. Accountemps, which is part of Robert Half International, surveyed more than 1,400 CFOs and 422 workers to obtain those results.

Accountemps chairman Max Messmer noted that the success or failure of an appraisal depends on how clearly both performance expectations and feedback are communicated to employees.

“Managers and their staff should be in agreement at the outset on what criteria will be used to evaluate effectiveness in a given role,” he said in a statement.

Performance reviews shouldn't be delivered just once a year, Messmer cautioned. “Nothing discussed in a formal evaluation should come as a surprise to the employee,” he said. “The best managers regularly give their teams performance feedback throughout the year.”