All of these are unrealistic assumptions but can largely be incorporated into the theory. For example, if the product is being sold in an imperfectly competitive market, there will not be a constant price for the product but marginal revenue product will still be obtained in the same way. If the productivity of labour changes, there will be a shift in the MRP curve. Despite the drawbacks of neo-classical theory, it has established that the firm will hire labour up to the point where the cost of hiring is equal to the revenue derived from hiring