Measurement of instability in multi-level MRP systems

Many researchers have addressed the issue of nervousness in schedules. Experimental studies dealing with this issue have focused mainly on single-level material requirements planning (MRP) systems and/or have been conducted under deterministic demand conditions. In these studies, nervousness is measured using various methods, in terms either of the frequency or the magnitude of changes in order quantity. The methods used in these studies were suitable for the particular operating environments that were being considered. Recently, a number of studies have been reported that evaluated schedule nervousness under more realistic conditions, such as in multi-level MRP systems under uncertain demand conditions. These studies have adopted some of the existing methods for measuring system nervousness. However, these methods do not capture all aspects of instability in multi-level MRP systems under uncertain demand conditions. In this article, we discuss the shortcomings of existing methods for measuring schedule nervousness, then present a new metric for measuring schedule nervousness in multi-level MRP environments. The proposed measure is illustrated by way of a detailed example. Results of simulation studies conducted to evaluate the effectiveness of the suggested method are also presented.