A firm, facing difficulties in monitoring its workers, hires an economic consultant to study the labour policies of the firm. The consultant prepares a report in which she recommends that the firm needs to raise employees' wages. At a meeting of the firm's managers to discuss the report, one manager makes the following argument: 'I think the wages we are paying are fine. As long as enough people are willing to work here at the wages we are currently paying, why should we raise them?' What argument can the economic consultant make to justify her advice that the firm should increase its wages?