During the review there are two ways you can look at the price adjustment. If for example you are looking at the purchase of plastics pots and you know the weight of raw materials that goes into each pot, then the movement in the price will directly correlate to the increase or decrease in the material cost. If you do not know the specific quantities of the index-linked item such as with fuel in transport, then the adjustment must be linked back to the price paid at the beginning of the contract as it will be based on percentage variations.