Figure 14 shows the resulting percentage savings, making it clear that if the OVTB increased, the savings grew too, although with a progressively reduced relative increment. The greatest savings increment was obtained passing from one to two weeks of OVTB. However, even if Figure 13 shows that the highest savings were obtained for 13 weeks of OVTB, it should be remarked that for many firms often it is almost impossible to know customers orders more than two or four weeks in advance.