One of the most common questions we are asked is how to sustain the
gains once we have improved the process. A lot of work went into getting
the process right in that carefully planned kaizen workshop, and it
is certainly wasteful to see it slip back to where it was before the change.
Unfortunately, the most common outcome of process improvements is
slipping backward. Why does this occur?
The problem is actually a fundamental misunderstanding of what
it means to sustain the gains. It goes back to our old friend machine
thinking. When you make an improvement to a machine, you expect
it to operate in the new improved state for some time, as long as some
basic maintenance is done. For example, you do not expect to make a
change that improves an engine’s output and then have it creep back
to the lower level of output within weeks, though even a technical change like
this does not last forever. On the other hand, when
you improve a socio-technical system, it is not just a physical thing
that you are changing. Let’s consider three examples of lean improvements
that are often made by staff experts:
1. Line rebalance. Rebalance the work on the line to a given takt in
order to increase productivity.
2. Standardized work. Develop new standardized work, emphasizing
quality key points, to reduce variability in order to improve
3. Pull system. Organize a supermarket area with defined minimum
and maximum inventory levels and a kanban system in order to
In each case, the improvement project may be great technically, with
superior visuals and precisely calculated quantities, yet still fail in the
long run. There are two problems. First, each of these projects is based
on the set of conditions at the time of the project, which in reality will
change over time. Second, each of these projects assumes a set of behaviors
by the people working in the area, which may in fact not occur.
One assumption of each of these lean projects is a certain rate of
customer demand—the takt. What if the customer demand changes?
Then you need to rebalance the work to a new takt, you need to
revise the standardized work based on a new takt, and you need to
identify the quantities in the supermarket based on the new takt.
Many other things can also change—the mix of products may vary,
there may be engineering changes to the product, parts may come and
go, customers may use different containers, and so on. Each of these
changes requires some adjustments. Unless the expert who set up the
system stays around indefinitely to make these adjustments, the system
will degrade. And unless the expert stays around to continually retrain
the workers and to monitor their behavior and provide feedback when
they stray from the standards, the system will degrade.
If we shift from machine thinking to systems thinking, we get a very
different perspective. It is well known in systems thinking that systems
are always changing, even when it appears that they are staying the
same. To maintain consistent output, one must continually adjust the
system to changing environmental conditions. This is called dynamic
homeostasis in systems thinking, or running to stay in place. Think of
the hamster madly running on a wheel and simply staying in one
place. If the hamster stops running, it will be carried backward by the
momentum of the wheel.
So asking how to sustain the gains is equivalent to asking what the
dynamics are that will keep the system in homeostasis. There are two
parts to the answer: (1) dynamic adjustment to changing conditions,
and (2) people being checked and coached on how well they follow the
The dynamic adjustment needed to keep the system stable is what
Toyota calls “’maintenance kaizen.’ It is well recognized at Toyota
that it takes a lot of work to maintain a system. And the dirty little
secret is that the more waste you take out of a system, the more work
it takes to maintain the system at that high level of performance.
Maintenance comes from having clearly defined standards, observing
carefully for deviations from those standards, and then developing
and implementing countermeasures to eliminate the deviations.
Sometimes a new standard is needed simply to maintain the quality
or safety or productivity because conditions have changed. It is really
hard work, and it can be done only on a continuous basis by someone
who is continually in the process so that he can closely monitor
it, which in most cases means the team members, team leaders, or
group leaders. This of course assumes you have a sufficient number of well
trained team leaders and group leaders, trained in kaizen, who are at the gemba observing, leading the people to
follow the current standards and call for help when there is a deviation, and adjusting the system.