MUDA, MURA, MURI are three terms often used together in the Toyota Production System (and called the Three Ms) that collectively describe wasteful practices to be eliminated.
Mura is the Japanese word for “unevenness, irregularity, lack of uniformity”. It describes “feast and famine” cycles of work when some periods are significantly busier than others. Mura is a barrier to flow.
Unevenness occurs in an agile team when there is a wide variety of sizes of Product Backlog items. The larger the item, the greater the inbuilt and hidden variability. Large items:
Unevenness often can be eliminated by teams through level scheduling and careful attention to the pace of work and the size of Backlog items.
The “no estimates” movement recommend slicing items into their smallest, consistent size. That is, slicing every Backlog Items into “Small” by the time it comes to a Sprint.
Kanban focuses on increasing workflow efficiency and helping teams to achieve continuous improvement. It uses several powerful tools for identifying areas of Mura within your process and working to eliminate them.
Visualisation is one of the key principles of the methodology – a picture is worth a thousand words. The Kanban board makes bottlenecks immediately apparent, and changes in the gradient of the cumulative flow diagram are a warning sign of problems brewing and increases in Mura. You can also use charts such as the cycle time scatterplot and throughput histogram to assess your level of Mura over time – more regular and consistent results means your efforts to reduce Mura are working.
Uneven and changing customer demands lead to Mura. Developing a Kanban roadmap to set your goals and directions, rather than planning in detail what tasks you will be working on six months from now. In the short-term, Product Managers and other stakeholders can then translate these goals into work items, prioritise them accordingly and feed them into the backlog. This lets your team pull tasks into the workflow at a steady pace. The Kanban Method suggests an approach to Backlog management that reduces the effort of maintaining your backlog and helps teams improve self-management.
Accumulation of lots of work in progress in any one process stage inevitably causes unevenness. Kanban work in progress limits are used to avoid this – new backlog items cannot be pulled into a process stage before an outstanding task has moved to the next stage. This can help you maintain a steady flow of tasks. Make sure to have explicit pull policies to ensure tasks enter and leave process stages in the same order, or your cycle times will become more variable.
Irregular working rhythms are a major cause of Mura. As mentioned above, this frequently occurs because of slow process stages affecting up and downstream stages. The theory of constraints states that the flow of a process can be no greater than its slowest stage – its constraint. Improving the constraint improves the flow, making the working rhythm smoother and more consistent.
There is no magic bullet to eliminate Mura from your workflow once and for all. There are hundreds of factors that can cause unevenness within your process, both within and out of your control. Nevertheless, making these incremental, iterative changes will have a cumulative effect – a more predictable and profitable process.
1. Siderova, S. (2019) Lean Manufacturing Wastes: Mura