Perfection
As organization begin to accurately specify value, identify the entire value stream, make the value-creating steps for specific products flow continuously, and let the customers pull value from the enterprise, something very odd begins to happen. It dawns on those involved that there is no end to the process of reducing effort, time, space, cost, and mistakes while offering a product which is ever more nearly what the customer actually wants. Suddenly perfection, the fifth and final principle of lean thinking, doesn't seem like a crazy idea.
Why should this be? Because the four initial principles interact with each other in a virtuous circle. Getting value to flow faster always exposes hidden muda in the value stream. And the harder you pull, the more impediments to flow are revealed so they can be removed. Dedicated product teams in direct dialogue with customers always find ways to specify value more acccurately and often learn ways to enhance flow and pull as well.
Bron: Lean Thinking, James P. Womack & Daniel T. Jones