Principles Of Lean Thinking
Principles of Lean Thinking
Mary Poppendieck
Poppendieck.LLC
7666 Carnelian Lane
Eden Prairie, MN 55346 USA
952-934-7998
mary@poppendieck.com
Abstract
shipping products the same day they were ordered was
a breakthrough concept when LL Bean upgraded its
In the 1980’s, a massive paradigm shift hit factories
distribution system in the late 1980’s. Southwest
Airlines, one of the few profitable airlines these days,
throughout the US and Europe. Mass production and
scientific management techniques from the early 1900’s
saves a lot of money with its unorthodox method of
were questioned as Japanese manufacturing companies
assigning seats as people arrive at the airport. Dell
demonstrated that ‘Just-in-Time’ was a better paradigm.
maintains profitability in a cutthroat market by
The widely adopted Japanese manufacturing concepts
manufacturing to order in less than a week. Another
came to be known as ‘lean production’. In time, the
Austin company builds custom homes in 30 days.
abstractions behind lean production spread to logistics,
and from there to the military, to construction, and to
The common denominator behind these and many other
the service industry. As it turns out, principles of lean
industry-rattling success stories is lean thinking. Lean
thinking are universal and have been applied
thinking looks at the value chain and asks: How can
successfully across many disciplines.
things be structured so that the enterprise does nothing
but add value, and does that as rapidly as possible? All
Lean principles have proven not only to be universal,
the intermediate steps, all the intermediate time and all
but to be universally successful at improving results.
the intermediate people are eliminated. All that’s left
When appropriately applied, lean thinking is a well-
are the time, the people and the activities that add value
understood and well-tested platform upon which to
for the customer.
build agile software development practices.
Origins of Lean Thinking
Introduction
Lean thinking got its name from a 1990’s best seller
Call a doctor for a routine appointment and chances are
called The Machine That Changed the World : The
it will be scheduled a few weeks later. But one large
Story of Lean Production1. This book chronicles the
HMO in Minnesota schedules almost all patients within
movement of automobile manufacturing from craft
a day or two of their call, for just about any kind of
production to mass production to lean production. It
medical service. A while ago, this HMO decided to
tells the story of how Henry Ford standardized
worked off their schedule backlogs by extending their
automobile parts and assembly techniques, so that low
hours, and then vary their hours slightly from week to
skilled workers and specialized machines could make
week to keep the backlog to about a day. True, the
cheap cars for the masses. The book goes on to
doctors don’t have the comforting weeks-long list of
describe how mass production provided cheaper cars
scheduled patients, but in fact, they see just as many
than the craft production, but resulted an explosion of
patients for the same reasons as they did before. The
indirect labor: production planning, engineering, and
patients are much happier, and doctors detect medical
management. Then the book explains how a small
problems far earlier than they used to.
company set its sights set on manufacturing cars for
Japan, but it could not afford the enormous investment
in single purpose machines that seemed to be required.
The idea of delivering packages overnight was novel
when Federal Express was started in 1971. In 1983, a
new company called Lens Crafters changed the basis of
1 The Machine That Changed the World : The Story of Lean
competition in the eyeglasses industry by assembling
Production, by Womack, James P., Daniel T. Jones, and
prescription glasses in an hour. The concept of
Daniel Roos, New York: Rawson and Associates; 1990.
Copyright © 2002 Poppendieck.LLC
Page 1
Nor could it afford the inventory or large amount of
produces a greater and ever growing variety of
indirect labor that seemed necessary for mass
products.”3
production. So it invented a better way to do things,
using very low inventory and moving decision-making
While on a tour of a large customer, Michael Dell saw
to production workers. Now this small company has
technicians customizing new Dell computers with their
grown into a large company, and the Toyota Production
company’s ‘standard’ hardware and software. “Do you
System has become known as ‘lean production’.
think you guys could do this for me?” his host asked.
Without missing a beat, Dell replied, “Absolutely, we’d
“The mass-producer uses narrowly skilled professionals
love to do that.”4 Within a couple of weeks, Dell was
to design products make by unskilled or semiskilled
shipping computers with factory-installed, customer-
workers tending expensive, single-purpose machines.
specific hardware and software. What took the
These churn out standardized products at high volume.
customer an hour could be done in the factory in
Because the machinery costs so much and is so
minutes, and furthermore, computers could be shipped
intolerant of disruption, the mass-producer adds many
directly to end-users rather than making a stop in the
buffers – extra supplies, extra workers, and extra space
corporate IT department. This shortening of the value
– to assure smooth production…. The result: The
chain is the essence of lean thinking.
customer gets lower costs but at the expense of variety
and by means of work methods that most employees
Companies that re-think the value chain and find ways
find boring and dispiriting.”2
to provide what their customers value with significantly
fewer resources than their competitors can develop an
Think of the centralized eyeglasses laboratory.
unassailable competitive advantage. Sometimes
Remember that Sears used to take two or three weeks to
competitors are simply not able to deliver the new value
fill orders from its once-popular catalog. Recall the
proposition. (Many have tired to copy Dell; few have
long distribution channel that used to be standard in the
succeeded.) Sometimes competitors do not care to
computer market. Think dinosaurs. Centralized
copy a new concept. (Southwest Airlines has not
equipment, huge distribution centers and lengthy
changed the industry’s approach to seat assignments.)
distribution channels were created to realize economies
Sometimes the industry follows the leader, but it takes
of scale. They are the side effects of mass-production,
time. (Almost all direct merchandise is shipped within a
passed on to other industries. What people tend to
day or two of receiving an order these days, but the
overlook is that mass-production creates a tremendous
Sears catalog has been discontinued.)
amount of work that does not directly add value.
Shipping eyeglasses to a factory for one hour of
Lean Thinking in Software Development
processing adds more handling time by far than the
processing time to make the glasses. Adding retail
distribution to the cutthroat personal computer industry
eBay is a company which pretty much invented ‘lean’
means that a manufacturer needs six weeks to respond
trading by eliminating all the unnecessary steps in the
to changing technology, instead of six days. Sears’
trading value chain. In the mid 1990’s, basic eBay
practice of building an inventory of mail orders to fill
software capabilities were developed by responding
meant keeping track of stacks of orders, not to mention
daily to customer requests for improvements.5
responding to innumerable order status queries and
Customers would send an e-mail to Pierre Omidyar
constant order changes.
with a suggestion and he would implement the idea on
the site that night. The most popular features of eBay,
those which create the highest competitive advantage,
“The lean producer, by contrast, combines the
were created in this manner.
advantages of craft and mass production, while
avoiding the high cost of the former and the rigidity of
the later… Lean production is ‘lean’ because it uses
Digital River invented the software download market in
less of everything compared with mass production –
the mid 1990’s by focusing on ‘lean’ software delivery.
half the human effort in the factory, half the
Today Digital River routinely designs and deploys
manufacturing space, half the investment in tools, half
the engineering hours to develop a new product in half
3 Womack (1990) p 13.
the time. Also, it requires keeping far less than half the
inventory on site, results in many fewer defects, and
4 Direct from Dell, by Michael Dell with Catherine Fredman,
Harper Business, 1999, p 159
5 Q&A with eBay's Pierre Omidyar, Business Week Online,
2
December 3, 2001.
Womack (1990) p 13.
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sophisticated web sites for corporate customers in a
Add Nothing But Value (Eliminate Waste)
matter of a weeks, by tying the corporation’s legacy
databases to standard front end components customized
The first step in lean thinking is to understand what
with a ‘look and feel’ specific to each customer.
value is and what activities and resources are absolutely
necessary to create that value. Once this is understood,
In the mid 1990’s, Microsoft implemented corporate-
everything else is waste. Since no one wants to
wide financial, purchasing and human resource
consider what they do as waste, the job of determining
packages linked to data warehouses which can be
what value is and what adds value is something that
accessed via web front-ends. Each was implemented
needs to be done at a fairly high level. Let’s say you
by “a handful of seasoned IT and functional experts…
are developing order tracking software. It seems like it
(who got) the job done in the time it takes a …
would be very important for a customer to know the
committee to decide on its goals.”6
status of their order, so this would certainly add
customer value. But actually, if the order is in house
In each of these examples, the focus of software
for less than 24 hours, the only order status that is
development was on rapid response to an identified
necessary is to inform the customer that the order was
need. Mechanisms were put in place to dramatically
received, and then that it has shipped, and let them
shorten the time from problem recognition to software
know the shipping tracking number. Better yet, if the
solution. You might call it ‘Just-in-Time’ software
order can be fulfilled by downloading it on the Web,
development.
there really isn’t any order status necessary at all.
The question is – why isn’t all software developed
To develop breakthroughs with lean thinking, the first
quickly? The answer is – rapid development must be
step is learning to see waste. If something does not
considered important before it becomes a reality. Once
directly add value, it is waste. If there is a way to do
speed becomes a value, a paradigm shift has to take
without it, it is waste. Taiichi Ohno, the mastermind of
place, changing software development practices from
the Toyota Production System, identified seven types of
the mass production paradigm to lean thinking.
manufacturing waste:
If your company writes reams of requirements
The Seven Wastes of Manufacturing
documents (equivalent to inventory), spends hours upon
hours tracking change control (equivalent to order
Overproduction
tracking), and has an office which defines and monitors
Inventory
the software development process (equivalent to
Extra Processing Steps
industrial engineering), you are operating with mass-
production paradigms. Think ‘lean’ and you will find a
Motion
better way.
Defects
Waiting
Basic Principles of Lean Development
Transportation
There are four basic principles of lean thinking which
are most relevant to software development:
Here is how I would translate the seven wastes of
manufacturing to software development:
The Basic Principles of Lean Development
The Seven Wastes of Software Development
Add Nothing But Value (Eliminate Waste)
Overproduction = Extra Features
Center On The People Who Add Value
Inventory = Requirements
Flow Value From Demand (Delay Commitment)
Extra Processing Steps = Extra Steps
Optimize Across Organizations
Motion = Finding Information
Defects = Defects Not Caught by Tests
Waiting = Waiting, Including Customers
6 Inside Microsoft: Balancing Creativity and Discipline,
Transportation = Handoffs
Herbold, Robert J.; Harvard Business Review, January 2002.
Copyright © 2002 Poppendieck.LLC
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Extreme Programming (XP) is a set of practices which
In the software industry, the same slogan “Do It Right
focuses on rapid software development. It is interesting
the First Time,” has been misused as an excuse to apply
to examine how XP works to eliminate the seven
mass-production thinking, not lean thinking to software
wastes of software development:
development. Under this slogan, responsibility has
been taken away from the developers who add value,
which is exactly the opposite of its intended effect.
Waste in Software
How Extreme Programming
“Do It Right the First Time” has been used as an excuse
Development
Addresses Waste
to insert reams of paperwork and armies of analysts and
Develop only for today’s
Extra Features
designers between the customer and the developer. In
stories
fact, the slogan is only properly applied if it gives
Story cards are detailed only
developers more, not less, involvement in the results of
Requirements
for the current iteration
their work.
Code directly from stories;
Extra Steps
get verbal clarification directly
A more appropriate translation of such slogans as “Zero
from customers
Defects” and “Do It Right the First Time” would be
“Test First”. In other words, don’t code unless you
Have everyone in the same
Finding Information
understand what the code is supposed to do and have a
room; customer included
way to determine whether the code works. A good
Defects Not
Test first; both developer
knowledge of the domain coupled with short build
Caught by Tests
tests and customer tests
cycles and automated testing constitute the proper way
for software developers to “Do It Right the First Time”.
Waiting, Including Deliver in small increments
Customers
Developers work directly with
Center On The People Who Add Value
Handoffs
customers
Almost every organization claims it’s people are
important, but if they truly center on those who add
‘Do It Right The First Time’
value, they would be able to say:
XP advocates developing software for the current need,
The people doing the work are the center of
and as more ‘stories’ (requirements) are added, the
design should be ‘refactored’7 to accommodate the new
Resources
stories. Is it waste to refactor software? Shouldn’t
Information
developers “Do It Right the First Time?”
Process Design Authority
It is instructive to explore the origins of the slogan “Do
Decision Making Authority
It Right the First Time.” In the 1980’s it was very
Organizational Energy
difficult to change a mass-production plant to lean
production, because in mass production, workers were
In mass-production, tasks are structured so that low
not expected to take responsibility for the quality of the
skilled or unskilled workers can easily do the repetitive
product. To change this, the management structure of
work, but engineers and managers are responsible for
the plant had to change. “Workers respond only when
production. Workers are not allowed to modify or stop
there exists some sense of reciprocal obligation, a sense
the line, because the focus is to maintain volume. One
that management actually values skilled workers, …
of the results of mass-production is that unskilled
and is willing to delegate responsibility to [them].”8
workers have no incentive to volunteer information
The slogan “Do It Right the First Time” encouraged
about problems with the manufacturing line or ways to
workers to feel responsible for the products moving
improve the process. Maladjusted parts get fixed at the
down the line, and encourage them to stop the line and
end of the line; a poor die or improperly maintained
troubleshoot problems when and where they occurred.
tool is management’s problem. Workers are neither
trained nor encouraged to worry about such things.
“The truly lean plant has two key organizational
7 Refactoring is improving the design of software without
features: It transfers the maximum number of tasks and
changing functionality.
responsibilities to those workers actually adding value
8 Womack (1990) p 99.
to the car on the line, and it has in place a system for
Copyright © 2002 Poppendieck.LLC
Page 4
detecting defects that quickly traces every problem,
This kind of thinking comes from mass-production,
once discovered, to its ultimate cause.”9 Similarly in
where skilled industrial engineers are expected to
any lean enterprise, the focus is on the people who add
design production work for unskilled laborers. It is the
value. In lean enterprises, traditional organizational
antithesis of lean thinking and devalues the skills of the
structures give way to new team-oriented organizations
developers who actually write the code as surely as
which are centered on the flow of value, not on
industrial engineers telling laborers how to do their jobs
functional expertise.
devalues the skills of production workers.
The first experiment Taiichi Ohno undertook in
Centering on the people who add value means
developing lean production was to figure out a way to
upgrading the skills of developers through training and
allow massive, single-purpose stamping machines to
apprenticeships. It means forming teams that design
stamp out multiple parts. Formerly, it took skilled
their own processes and address complete problems. It
machinists hours, if not days, to change dies from one
means that staff groups and managers exist to support
part to another. Therefore, mass production plants had
developers, not to tell them what to do.
many single purpose stamping machines in which the
dies were almost never changed. Volume, space, and
Flow Value From Demand
financing were not available in Japan to support such
(Delay Commitment)
massive machines, so Ohno set about devising simple
methods to change the stamping dies in minutes instead
of hours. This would allow many parts of a car to be
The idea of flow is fundamental to lean production. If
made on the same line with the same equipment. Since
you do nothing but add value, then you should add the
the workers had nothing else to do while the die was
value in as rapid a flow as possible. If this is not the
being changed, they also did the die changing, and in
case, then waste builds up in the form of inventory or
fact, the stamping room workers were involved in
transportation or extra steps or wasted motion. The
developing the methods of rapid die changeover.
idea that flow should be ‘pulled’ from demand is also
fundamental to lean production. ‘Pull’ means that
Ohno transferred most of the work being done by
nothing is done unless and until a downstream process
engineers and managers in mass-production plants to
requires it. The effect of ‘pull’ is that production is not
the production workers. He grouped workers in small
based on forecast; commitment is delayed until demand
teams and trained the teams to do their own industrial
is present to indicate what the customer really wants.
engineering. Workers were encouraged to stop the line
if anything went wrong, (a management job in mass-
Pulling from demand can be one of the easiest ways to
production). Before the line was re-started, the workers
implement lean principles, as LL Bean and Lens
were expected to search for the root cause of the
Crafters and Dell found out. The idea is to fill each
problem and resolve it. At first the line was stopped
customer order immediately. In mass-production days,
often, which would have been a disaster at a mass-
filling orders immediately meant building up lots of
production plant. But eventually the line ran with very
inventory in anticipation of customer orders. Lean
few problems, because the assembly workers felt
production changes that. The idea is to be able to make
responsible to find, expose, and resolve problems as
the product so fast that it can be made to order. True,
they occurred.
Dell and Lens Crafters and LL Bean and Toyota have to
have some inventory of sub-assemblies waiting to be
It is sometimes thought that a benefit of good software
turned into a finished product at a moments notice.
engineering is to allow low skilled programmers to
But it’s amazing how little inventory is necessary, if the
produce code while a few high skilled architects and
process to replenish the inventory is also lean. A truly
designers do the critical thinking. With this in mind, a
lean distribution channel only works with a really lean
project is often divided into requirements gathering,
supply chain coupled to very lean manufacturing.
analysis, design, coding, testing, and so on, with
decreasing skill presumably required at each step. A
The “batch and queue” habit is very hard to break. It
‘standard process’ is developed for each step, so that
seems counterintuitive that doing a little bit at a time at
low-skilled programmers, for example, can translate
the last possible moment will give faster, better,
design into code simply by following the process.
cheaper results. But anyone designing a control system
knows that a short feedback loop is far more effective at
maintaining control of a process than a long loop. The
problem with batches and queues is that they hide
problems. The idea of lean production is to expose
9 Womack (1990) p 99. Italics in the original.
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problems as soon as they arise, so they can be corrected
For example, let’s say that the ultimate performance
immediately. It may seem that lean systems are fragile,
measurement of a stamping room is machine
because they have no padding. But in fact, lean
productivity. This measurement motivates the
systems are quite robust, because they don’t hide
stamping room to build up mounds of inventory to keep
unknown, lurking problems and they don’t pretend they
the machines running at top productivity. It does not
can forecast the future.
matter that the inventory has been shown to degrade the
overall performance of the organization. As long as the
In Lean Software Development, the idea is to maximize
stamping room is measured primarily on machine
the flow of information and delivered value. As in lean
productivity, it will build inventory. This is what is
production, maximizing flow does not mean
known as a sub-optimizing measurement, because it
automation. Instead, it means limiting what has to be
creates behavior which creates local optimization at the
transferred, and transferring that as few times as
expense of overall optimization.
possible over the shortest distance with the widest
communication bandwidth as late as is possible.
Sub-optimizing measurements are very common, and
Handing off reams of frozen documentation from one
overall optimization is virtually impossible when they
function to the next is a mass-production mentality. In
are in place. One of the biggest sub-optimizing
Lean Software Development, the idea is to eliminate as
measurements in software development occurs when
many documents and handoffs as possible. Documents
project managers are measured on earned value.
which are not useful to the customer are replaced with
Earned value is the cost initially estimated for the tasks
automated tests. These tests assure that customer value
which have been completed. The idea is that you had
is delivered both initially and in the future when the
better not have spent any more than you estimated. The
inevitable changes are needed.
problem is, this requires a project manager to build up
an inventory of task descriptions and estimates. Just as
In addition to rapid, Just-in-Time information flow,
excess inventory in the stamping room slows down
Lean Software Development means rapid, Just-in-Time
production and degrades over time, the inventory of
delivery of value. In manufacturing, the key to
tasks required for earned value calculations gets in the
achieving rapid delivery is to manufacture in small
way of delivering true business value and also degrades
batches pulled by a customer order. Similarly in
over time. Nevertheless, if there is an earned value
software development, the key to rapid delivery is to
measurement in place, project tasks are specified and
divide the problem into small batches (increments)
estimated, and earned value is measured. When it
pulled by a customer story and customer test. The
comes to a choice between delivering business value or
single most effective mechanism for implementing lean
earned value (and it often does), earned value usually
production is adopting Just-in-Time, pull-from-demand
wins out.
flow. Similarly, the single most effective mechanism
for implementing Lean Development is delivering
To avoid these problems, lean organizations are
increments of real business value in short time-boxes.
usually structured around teams that maintain
responsibility for overall business value, rather than
In Lean Software Development, the goal is to eliminate
intermediate measurements such as their ability to
as many documents and handoffs as possible. The
speculate and pad estimates. Another approach is to
emphasis is to pair a skilled development team with a
foster a keen awareness that the downstream
skilled customer team and give them the responsibility
department is a customer, and satisfying this internal
and authority to develop the system in small, rapid
customer is the ultimate performance measurement.
increments, driven by customer priority and feedback.
The paradigm shift that is required with lean thinking is
Optimize across Organizations
often hindered if the organization is not structured
around the flow of value and focused on helping the
customer pull value from the enterprise. For this
Quite often, the biggest barrier to adopting lean
reason, software development teams are best structured
practices is organizational. As products move from one
around delivering increments of business value, with all
department to another, a big gap often develops,
the necessary skills on the same team (eg. customer
especially if each department has its own set of
understanding / domain knowledge, architecture /
performance measurements that are unrelated to the
design, system development, database administration,
performance measurements of neighboring
testing, system administration, etc.).
departments.
Copyright © 2002 Poppendieck.LLC
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Software Development Contracts
fairness, stability, and predictability of [the company’s]
routines and processes.”12
Flow along the value stream is particularly difficult
when multiple companies are involved. Many times I
It has been the practice of legal departments writing
have heard the lament: “Everything you say makes
software contracts to put into contractual language all
sense, but it is impossible to implement in our
of the protections necessary to keep the other side
environment, because we work under contracts with
‘honest.’ However, the transaction costs associated
other organizations.” Indeed, the typical software
with creating and monitoring such contracts are
development contract can be the ultimate sub-
enormous. Many contracts all but demand a waterfall
optimizing mechanism. Standard software contracts
process, even if both companies believe this is not the
and supplier management practices have a tendency to
best approach. It’s time that the software development
interfere with many lean principles.
industry learned the lesson of Supply Chain
Management – “Extraordinary productivity gains in the
production network or value chain are possible when
Manufacturing organizations used to have the same
companies are willing to collaborate in unique ways,
problem. For example, US automotive companies once
often achieving competitive advantage by sharing
believed the best way to reduce the cost of parts in an
resources, knowledge, and assets…. Today
automobile was with annual competitive bidding. If the
competition occurs between value chains and not
only thing that is important is cheap parts, competitive
simply between companies.”13
bidding may seem like the best way to achieve this
goal. However, if overall company performance is
more important, then better parts which integrate more
Summary and Conclusion
effectively with the overall vehicle are more valuable.
In fact, there is an direct correlation between an
The lean production metaphor is a good one for
automotive company’s profitability and its degree of
software development, if it is applied in keeping with
collaboration with suppliers.10 When Chrysler moved
the underlying spirit of lean thinking. In the past, the
from opportunistic to collaborative relationships with
application of some manufacturing concepts to software
its suppliers in the late 1990’s, it’s performance
development (‘Do It Right the First Time’ comes to
improved significantly.
mind) may have lacked a deep understanding of what
makes lean principles work. The underlying principles
The software industry has some lessons to learn in the
of eliminating waste, empowering front line workers,
area of contractual agreements between organizations.
responding immediately to customer requests, and
It needs to learn how to structure collaborative
optimizing across the value chain are fundamental to
relationships which maximize the overall results of both
lean thinking. When applied to software development,
parties. A key lesson the software industry needs to
these concepts provide a broad framework for
learn is how to structure contracts for incremental
improving software development.
deliveries that are not pre-defined in the contract, yet
assure the customer of prompt delivery of business
value appropriate to their investment. Here again, we
can learn from lean production.
Lean manufacturing organizations develop a limited
number of relationships with ‘trusted’ suppliers, and in
turn, gain the ‘trust’ of these suppliers. What does
‘trust’ mean? “Trust [is] one party’s confidence that
the other party in the exchange relationship will fulfill
its promises and commitments and will not exploit its
vulnerabilities.”11 “…trust…[is] not based on greater
interpersonal trust, but rather greater trust in the
10 Collaborative Advantage, by Jeffrey H. Dyer, Oxford
University Press; 2000, p 6.
12 Dyer (2000) p 100
11 Dyer (2000) p 88.
13 Dyer (2000) p 5
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