Maintaining high levels of customer service carries heavy costs and can only be justified when doing so results in marketing opportunities which otherwise would not be realised. At the same time, the logistics manager must monitor the effects of operating a given level of customer service on profitability. As figure 9.5 seeks to illustrate, as the customer service level gets nearer to 100 percent, the costs of doing so rise sharply. This means considering the trade-offs between the costs involved and the service level offered. It is possible, after all, to provide a level of service above that required or appreciated by the customer. There is likely to be no discernible difference in the service levels of two suppliers, one of whom is able to immediately supply a spare part from stock on 99 of 100 occasions and another who is able to supply from stock on 97 of 100 occasions.