The aim of benchmarking and market testing is to provide a means of sharing the risk that costs or possibly revenues may change over the course of the Contract for reasons outside the Contractor's control. Either approach may result in an increase or decrease in the Unitary Charge that can be charged by the Contractor. The mechanism for making any such adjustment will be set out in the Contract and the Contractor should make sure it involves its financial advisers when making this calculation. Market testing is generally considered to be preferable to benchmarking and the WIDP Contract (Clause 34) mandates the use of market testing in preference to benchmarking if there is are a sufficient number bidders to generate a reasonably competitive market for the relevant services.