Quantity choice in unit price contract procurements

A common approach for procuring large construction projects is through Unit Price Contracts. By the means of a simple model, we study the optimal quantity to procure under uncertainty regarding the actual required quantity given that the procurer strives to minomize expected total costs. The model shows that the quantity to procure in optimum follows from a trade-off between the risk of having to pay for more units than actually necessary and of having to conduct costly renogotiations. The optimal quantity increases in costs associated with possible renegotiations, decreases in expected per unit price, and, if a renegotiation does not increase per unit price too much, decreases in the uncertainty surrounding the actual quantity required.