“…These studies assumed that research results on single-product lean manufacturing environments are scalable to multi-product lean manufacturing environments. This assumption is not reliable because a pure implementation of a PPCS in a multi-product environment requires maintaining semi-finished parts of each of the products distributed throughout the system, which proliferates WIP inventory (Olaitan & Geraghty, 2013;Onyeocha, 2012Onyeocha, , 2014Onyeocha, Khoury, & Geraghty, 2013, 2015Satyam & Krishnamurthy, 2008).…”