Professor David Simchi-Levi and doctoral student Yehua Wei applied a combination of optimization and stochastic methodologies to explain the effectiveness of “long chain” flexibility design in manufacturing operations. With the long chain design, manufacturing plants are endowed with the capacity to produce exactly two different products and every product is produced by exactly two plants. The design can be applied to other systems, including the cross-training of workers on an assembly line, supply chains, queuing networks, and people and tasks in a call center. But until now, nobody had explained or proved mathematically why the long chain works better than other flexibility models. Read the December issue of On Balance.