1 INTRODUCTION

We would like to express our deepest gratitude to Wally Hopp, Mark Spearman, and the eight commentators—all luminaries in Lean—for their excellent Forum articles (Hopp & Spearman 2021, hereinafter, source “A”; Cusumano et al. 2021, hereinafter, source “B”). These articles have stimulated thinking and encouraged rich debate in our community.

Over the past 40 years, Lean and the Toyota Production System (TPS) from which it originated have sourced much of the research on how to manage, improve, and connect operations. What began as a term chosen to highlight some salient characteristics of the TPS has evolved into a broad description of everything that improves operations management (OM). Yet, despite decades of effort, our two Forum articles show that scholars still do not agree on what Lean is. Should there be a difference between operational excellence (a general ideal) and Lean (a particular way to achieve it under particular circumstances)? When anything that improves OM and inter-operational connections is classified as Lean, do we lose sight of key tradeoffs that underlie competitive advantage? How do we reconcile Lean as operational excellence with the new appreciation of the value of “fat”—capacity or inventory buffers held to protect against variability or extreme events—under the current increase in recognition of the value of resilience in the OM community? Proponents of Lean claim that it has evolved much over the past 40 years, even apart from the TPS—but, in its evolution, when does Lean outgrow its name? In this editorial our aim is to be provocative and “stir the waters,” seeking to direct and deploy the energy generated by the exciting conversation started by these two Forum articles into a research agenda.

Both of us have worked closely with the TPS and Lean for most of our careers. Suzanne began her doctorate at the Harvard Business School (HBS) in 1982 with the intention of studying decision theory. She took a course by Professor Bob Hayes just as the shock of the success of the TPS hit the academic world. The excitement of trying to understand what about the TPS led to its highly counterintuitive and surprising global competitive advantage led Suzanne to switch her field to OM. At this time, the key insights discussed included the new understanding of the importance of shop-floor operators and quality management to successful OM—and the essential role that OM plays in competitiveness. Hall's Zero Inventories (Hall, 1983) had not yet been published, but a photocopy of an early version was being actively discussed by the entire HBS operations department. Schonberger's Japanese Manufacturing Techniques (1982) had just been published. Hayes had recently published “Why Japanese Factories Work” (Hayes, 1981). There was a keen awareness that what was being observed could not be explained by strategy theory, which led to urgent sensemaking organized around the idea of producing just in time (JIT), usually considered in conjunction with Total Quality Management (TQM). Much of the discussion centered around culture, and whether the ability to produce JIT with close-to-perfect quality could be achieved outside of Japan. Schonberger (1982), Hall (1983), and Monden (1983) prioritized the reduction of in-process inventory that causes one workstation to block or starve another (see Schonberger's figures 2 and 3 for a complete explanation of the proposed causal mechanisms, p. 26). Suzanne's research focused on this exploratory stress: When is such a line stoppage expected to lead to process improvement, and when does it just cause lost production—or worse, discouragement and demotivation? Proposing theory about the relationship between line stoppages and learning required Suzanne to propose a definition of a JIT system that permitted determination of whether a given system was JIT or not. While all systems seek to deliver on time (not be late), what is unique to JIT is that it sets the objective of being neither late nor early. A JIT system was thus defined (de Treville, 1987) as one that has a “flow-control” mechanism that prevents production in the absence of a downstream signal.

Later that decade, sensemaking about the TPS had evolved into Lean production, with the publication of The Machine that Changed the World (Womack et al., 1990) stemming from the International Motor Vehicle Program (IMVP) at the Massachusetts Institute of Technology (MIT). A relative of the IMVP at MIT, the Lean Aircraft (later, Aerospace) Initiative (LAI), launched Tyson's academic career. Like the IMVP, the LAI also led to a book (Murman et al., 2002). LAI supported Tyson throughout his graduate studies in the mid-1990s and provided him with access to its sponsor companies for the data foundational to both his master's and doctoral theses. Tyson thus could observe how Lean was being applied at companies such as Boeing, General Electric, Lockheed Martin, Northrop Grumman, Raytheon, and Texas Instruments. During most of this time, he was part of the Product Development Focus Group—one of five within LAI—exploring research questions about how Lean might apply in that context. Later on, as an assistant professor, Tyson had a unique opportunity to study Lean implementation in the F-22 program at Lockheed Martin, which led to a paper in this journal (Browning & Heath, 2009).

Thus, we have both witnessed firsthand the power of Lean practices and thinking to marshal resources around important research and applications. That said, our industry experiences and other research over the past couple of decades have given us a clear picture of how a failure to study Lean as a set of formal concepts that are precisely defined can impede understanding and communication. We have also observed weaknesses in our ability as a field to do effective research and sensemaking on this key topic. Our intent in this editorial is to map out a path to a formal conceptual definition of elements commonly ascribed to Lean, following the eight rules proposed by Wacker (2004). We then revisit one of the most highly cited articles about Lean—Shah and Ward (2003)—to explicate its contribution and explore the work done as a foundation for rigorous definition development. This analysis lets us propose a path toward (1) identifying, rigorously defining, and exploring operational attributes that underlie Lean and operational excellence, (2) disambiguating Lean from operational excellence, and (3) distinguishing between theory that captures tradeoffs between (i) Lean attributes and (ii) conceptual exploration—pre-theory—that underlies Lean thinking and Lean as a philosophy.

中文翻译：

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精益的精益观

1 介绍

我们要向 Wally Hopp、Mark Spearman 和 8 位评论员——所有精益领域的杰出人物——表示最深切的感谢，感谢他们在论坛上发表的出色文章（Hopp & Spearman 2021，下文中，来源“A”；Cusumano 等人，2021，下文中） ，来源“B”）。这些文章激发了我们社区的思考并鼓励了丰富的辩论。

在过去的 40 年里，精益及其起源的丰田生产系统 (TPS) 已经获得了大量关于如何管理、改进和连接运营的研究。最初选择强调 TPS 的一些显着特征的术语已经演变成对改进运营管理 (OM) 的一切的广泛描述。然而，尽管经过了几十年的努力，我们在论坛上的两篇文章表明，学者们对精益是什么仍然存在分歧。卓越运营（一般理想）和精益（在特定情况下实现它的特定方式）之间是否应该有区别？当任何改善 OM 和互操作连接的东西都被归类为精益时，我们是否忽略了构成竞争优势的关键权衡？在当前对 OM 社区弹性价值的认识不断增加的情况下，我们如何将精益作为卓越运营与对“脂肪”价值的新认识（为防止可变性或极端事件而持有的容量或库存缓冲）相协调？精益的支持者声称它在过去的 40 年里发生了很大的变化，即使不包括 TPS——但是，在它的演变过程中，精益什么时候超越了它的名字？在这篇社论中，我们的目标是具有挑衅性和“搅动水”，寻求将这两篇论坛文章引发的激动人心的对话所产生的能量引导和部署到研究议程中。

在我们的大部分职业生涯中，我们都与 TPS 和精益密切合作。Suzanne 于 1982 年开始在哈佛商学院 (HBS) 攻读博士学位，目的是研究决策理论。正当 TPS 的成功震惊学术界时，她参加了 Bob Hayes 教授的课程。试图了解 TPS 导致其高度违反直觉和令人惊讶的全球竞争优势的原因的兴奋促使 Suzanne 将她的领域转向 OM。此时，讨论的主要见解包括对车间操作员和质量管理对成功 OM 的重要性的新理解，以及 OM 在竞争力中发挥的重要作用。霍尔的零库存（霍尔，1983) 尚未出版，但整个 HBS 运营部门正在积极讨论早期版本的影印本。Schonberger 的日本制造技术(1982) 刚刚出版。Hayes 最近出版了“Why Japanese Factories Work”（Hayes，1981）。人们敏锐地意识到，所观察到的东西无法用战略理论来解释，这导致围绕及时生产 (JIT) 的想法组织起来的紧急意义构建，通常与全面质量管理 (TQM) 一起考虑。大部分讨论都围绕着文化，以及是否可以在日本以外实现生产接近完美质量的 JIT 的能力。勋伯格 ( 1982 ), 霍尔 ( 1983)) 和 Monden ( 1983)) 优先减少导致一个工作站阻塞或饿死另一个工作站的在制品库存（请参阅 Schonberger 的图 2 和图 3 以获取对提议的因果机制的完整解释，第 26 页）。Suzanne 的研究集中在这种探索性压力上：这种生产线停工预计什么时候会导致流程改进，什么时候只会导致生产损失——或者更糟的是，会导致气馁和士气低落？提出关于生产线停工和学习之间关系的理论要求 Suzanne 提出 JIT 系统的定义，该定义允许确定给定系统是否为 JIT。虽然所有系统都力求按时交付（不迟到），但 JIT 的独特之处在于它设定了既不迟也不早的目标。因此定义了 JIT 系统（de Treville，1987) 作为一种“流量控制”机制，可以在没有下游信号的情况下阻止生产。

那十年后期，关于 TPS 的意义建构已经演变成精益生产，随着麻省理工学院 (MIT) 国际机动车辆计划 (IMVP)的出版《改变世界的机器》（Womack 等人，1990 年） ）。麻省理工学院 IMVP 的亲戚，精益飞机（后来的航空航天）倡议 (LAI)，开启了泰森的学术生涯。像 IMVP 一样，LAI 也导致了一本书（Murman et al., 2002）。LAI 在 1990 年代中期的整个研究生学习期间为泰森提供支持，并为他提供访问其赞助公司的机会，以获取他的硕士和博士论文的基础数据。因此，泰森可以观察到精益在波音、通用电气、洛克希德马丁、诺斯罗普格鲁曼、雷神和德州仪器等公司的应用情况。在这段时间的大部分时间里，他是产品开发焦点小组的成员——LAI 的五个成员之一——探索有关精益如何在这种情况下应用的研究问题。后来，作为助理教授，泰森有一个独特的机会在洛克希德马丁公司研究 F-22 计划中的精益实施，这导致了该期刊上的一篇论文（Browning & Heath，2009 年）。

因此，我们都亲眼目睹了精益实践和思考围绕重要研究和应用整合资源的力量。也就是说，我们过去几十年的行业经验和其他研究让我们清楚地了解，如果未能将精益研究为一组精确定义的正式概念，会阻碍理解和沟通。我们还观察到我们作为一个领域在这个关键主题上进行有效研究和意义建构的能力存在弱点。我们在这篇社论中的意图是按照 Wacker ( 2004 年)提出的八项规则，为通常归因于精益的元素的正式概念定义制定一条路径。然后，我们重温了一篇关于精益的引用率最高的文章——Shah 和 Ward（2003 年）)——阐明其贡献并探索作为严格定义发展基础的工作。这种分析让我们提出了一条路径：(1) 识别、严格定义和探索作为精益和卓越运营基础的运营属性，(2) 消除精益与卓越运营的歧义，以及 (3) 区分捕捉 (i)精益属性和 (ii) 概念探索——前理论——是精益思想和精益哲学的基础。