King (1989) describes the complexity of budgeting for information systems in a constantly changing environment. He indicates that the budget development process requires an analysis of current activities, a projection of activities that will occur in the future, as well as an estimate of the resources required to support future planned activities. He states that the degree of stability within an environment is affected by changes in the mission of the department, costs of inputs to production, the degree to which increased needs for one input increase that for another (input complementarity), and the degree to which one input can be used to replace others (input substitutability).