Lean manufacturing

Lean manufacturing, or lean production, is a production method derived from Toyota's 1930 operating model "The Toyota Way" (Toyota Production System, TPS). The term "Lean" was coined in 1988 by John Krafcik, and defined in 1996 by James Womack and Daniel Jones to consist of five key principles: 'Precisely specify value by specific product, identify the value stream for each product, make value flow without interruptions, let customer pull value from the producer, and pursue perfection.' (Womack and Jones 1996 p10)
History.
Insights relating to value streams, efficiency (reduction of "waste"), continuous improvement and standardised products can most likely be traced back to the beginning of humankind. However, Fredrick Taylor and Henry Ford documented their observations relating to these topics, and Shigeo Shingo and Taiichi Ohno applied their enhanced thoughts on the subject at Toyota in the 1930s. The resulting methods were researched from the mid-20th century and dubbed "Lean" by John Krafcik in 1988, and then were defined in "The Machine that Changed the World" (Womack, Jones and Roos 1990) and further detailed by James Womack and Daniel Jones in "Lean Thinking" (1996).
Shigeo Shingo takes part of Frederick Taylor's views in 1910.
American industrialists recognized the threat of cheap offshore labor to American workers during the 1910s, and explicitly stated the goal of what is now called lean manufacturing as a countermeasure. Henry Towne, past President of the American Society of Mechanical Engineers, wrote in the Foreword to Frederick Winslow Taylor's "Shop Management" (1911), "We are justly proud of the high wage rates which prevail throughout our country, and jealous of any interference with them by the products of the cheaper labor of other countries. To maintain this condition, to strengthen our control of home markets, and, above all, to broaden our opportunities in foreign markets where we must compete with the products of other industrial nations, we should welcome and encourage every influence tending to increase the efficiency of our productive processes."
Continuous production improvement and incentives for such were documented in Taylor's Principles of Scientific Management (1911): 
Shingo cites reading "Principles of Scientific Management" in 1931 and being "greatly impressed to make the study and practice of scientific management his life's work"., 
Toyota's Production Systems (TPS) is born in the 1930s.
Shingo and Ohno were key to the design of Toyota's manufacturing process. Previously a textile company, Toyota moved into building automobiles in 1934. Kiichiro Toyoda, founder of Toyota Motor Corporation, directed the engine casting work and discovered many problems in their manufacturing, with wasted resources on repair of poor-quality castings. Toyota engaged in intense study of each stage of the process. In 1936, when Toyota won its first truck contract with the Japanese government, the processes encountered new problems, to which Toyota responded by developing "Kaizen" improvement teams (see The Toyota Way).
Ohno at Toyota brought the concepts together, building on the existing internal schools of thought, and spreading their breadth and use into what has become the Toyota Production System (TPS). It is principally from the TPS (referred to in the 1980s as just-in-time manufacturing or JIT), but now including many other sources, that lean production is developing.
Levels of demand in the postwar economy of Japan were low; as a result, the focus of mass production on lowest cost per item via economies of scale had little application. Having visited and seen supermarkets in the United States, Ohno recognised that scheduling of work should not be driven by sales or production targets but by actual sales. Given the financial situation during this period, over-production had to be avoided, and thus the notion of "pull" (or "build-to-order" rather than target-driven "push") came to underpin production scheduling.
TPS is translated into "Lean" 1988 by John Krafcik.
John Krafcik coined the term "Lean" in his 1988 article, "Triumph of the Lean Production System". The article states: (a) Lean manufacturing plants have higher levels of productivity/quality than non-Lean and (b) "The level of plant technology seems to have little effect on operating performance" (page 51). According to the article, risks with implementing Lean can be reduced by: "developing a well-trained, flexible workforce, product designs that are easy to build with high quality, and a supportive, high-performance supplier network" (page 51).
Method.
Key principles and waste.
Womack and Jones define Lean as "...a way to do more and more with less and less - less human effort, less equipment, less time, and less space - while coming closer and closer to providing customers exactly what they want" and then translate this into five key principles:
Lean is founded on the concept of continuous and incremental improvements on product and process while eliminating redundant activities. "The value of adding activities are simply only those things the customer is willing to pay for, everything else is waste, and should be eliminated, simplified, reduced, or integrated".
On principle 2, waste, see seven basic waste types under The Toyota Way. Additional waste types are: 
Implementing the method.
Senpai and Kohai 'coaching' claimed to have been used to implement The Toyota Way and rumoured as useful to also implement Lean.
For application of Lean to services rather than manufacturing, see Lean Services.
Criticism.
Critics of Lean argue that this management method has significant drawbacks, especially for the employees of companies operating under Lean. Common criticism of Lean is that it fails to take in consideration the employee's safety and well-being. Lean manufacturing is associated with an increased level of stress among employees, who have a small margin of error in their work environment which require perfection. Lean also over-focuses on cutting waste, which may lead management to cut sectors of the company that are not essential to the company's short-term productivity but are nevertheless important to the company's legacy. Lean also over-focuses on the present, which hinders a company's plans for the future.
Critics also make negative comparison of Lean and 19th century scientific management, which had been fought by the labor movement and was considered obsolete by the 1930s. Finally, lean is criticized for lacking a standard methodology: "Lean is more a culture than a method, and there is no standard lean production model."