Since the systems that are put in place are updated infrequently (because of the
costs of reinterviewing and resurveying), the model’s estimates of process, product, and customer costs soon become inaccurate. What’s more, people waste their time arguing about the accuracy of cost-driver rates that are derived from individuals’ subjective beliefs rather than addressing the deficiencies the model reveals: inefficient processes, unprofitable products and customers, and excess capacity.