Note---Comments on the Complexity Rating Factor for Layout Problems

In a recently published Note, Block (Block, T. E. 1979. On the complexity of facilities layout problems. Management Sci. 25 (3) 280--285.) attempted to provide a definitive method to evaluate the complexity of facilities layout problems. He proposed a complexity rating factor that is based on flow dominance and the number of facilities. Mathematically, the rating factor suffers from the use of an incorrect upper bound for flow dominance. Also, there is a problem with regard to its interpretability. These shortcomings are discussed in this Note. The sensitivities of flow dominance and the rating factor to changes in a single element of the flow matrix are examined and their implications discussed.