Equal treatment for comparable cases. This is contrasted with discrimination, which is differences of treatment on what are considered irrelevant grounds. In employment, for example, non-discrimination implies not choosing employees on grounds of sex, race, or religion, for positions where these grounds are not directly relevant to the duties to be performed. In international trade, non-discrimination means treating all transactions with non-nationals equally. The question of what differences are in fact irrelevant gives rise to problems: the principle of non-discrimination may conflict with actuarial evidence. In pensions, for example, it is an actuarial fact that women on average live longer than men; whether they should therefore receive lower pensions for equal contributions is a subject of controversy.