The comparison between employees in different positions, not only managers, should be carried out on the basis of objective and gender-neutral criteria. The Directive identifies four criteria: skills, effort, responsibility and working conditions. The employer may also define other relevant criteria such as workload, complexity of tasks, performance and others. The purpose of applying the criteria is to compare the value of the work, because the job functions are clearly different, and to determine which employees perform work of equal value and should therefore be paid equally.