A Cost Driver is any activity that causes a cost to be incurred. The Activity Based Costing (ABC) approach relates indirect cost to the activities that drive them to be incurred. In traditional costing the cost driver to allocate indirect cost to cost objects was volume of output. With the change in business structures, technology and thereby cost structures it was found that the volume of output was not the only cost driver. Some examples of indirect costs and their drivers are: maintenance costs are indirect costs and the possible driver of this cost may be the number of machine hours; or, handling raw-material cost is another indirect cost that may be driven by the number of orders received; or, inspection costs that are driven by the number of inspections or the hours of inspection or production runs. Generally, the cost driver for short term indirect variable costs may be the volume of output/ activity; but for long term indirect variable costs, the cost drivers will not be related to volume of output/ activity. John Shank and Vijay Govindarajan list cost drivers into two categories: Structural cost drivers that are derived from the business strategic choices about its underlying economic structure such as scale and scope of operations, complexity of products, use of technology, etc and Executional cost drivers that are derived from the execution of the business activities such as capacity utilization, plant layout, work-force involvement, etc. To carry out a value chain analysis, ABC is a necessary tool. To carry out ABC, it is necessary that cost drivers are established for different cost pools.