Aging Work in Progress: Are Tasks Staying in Your Flow too Long?

Limiting work in progres is a core principle of Kanban known as WIP limits. WIP limits allows teams to focus on current tasks in order to finish them faster. While limiting what team members work on, we must also be mindful of how long a task is in progress. If a task is being worked on for too long and it’s not coming out of the pipeline, it’s an indication of delay in your process.

In order to keep our workflow stable and steady, we need to to monitor how long a task stays in progress. This is what aging work in progress is about or what we call WIP aging.

What is WIP Aging?

WIP age is the amount of time that it takes to complete a task. This is usually measured in days. This key metric in Kanban is a good indicator of team capacity and process performance. On the other hand, WIP aging monitoring is the process used to analyze the flow of your tasks in your Kanban system using WIP age.

Benefits of Tracking Aging WIP

The amount of time spent in each of your in-progress states will vary based on the complexity of the task. Knowing how much time each task stays In Progress can help you spot issues, improve your flow, and estimate your team capacity.

• Spot issues before they escalate – Immediately recognize tasks that are taking longer than expected through your board or a WIP aging chart. Knowing this can trigger needed investigations and analysis. Some causes of longer WIP age could be work overload, unclear requirements, pending business feedback or decision, or inadequate skills to do the job.
• Make your flow more stable – Lowering your WIP age requires the streamlining of your process. Remove bottlenecks and unnecessary steps. This will increase the predictability and efficiency of your team’s performance and output.
• Estimate your team’s capacity based on similar contexts – Historical data on your WIP age can help team leaders plan their team’s capacity for current and future projects. A key consideration here though is the similarity of the tasks in terms of context for more accuracy and reliability.
• Know if you’re improving – As you lower your WIP age, it can be an indication of better performance. Just make sure that you cross-examine this with the level of quality of your team’s output. It’s important that quality is maintained while faster delivery is achieved.

How to Track Aging WIP

An aging WIP chart is used to track your tasks’ WIP age. The horizontal axis in a WIP chart shows the stages in your Kanban system while the vertical axis shows the number of days a task is in progress. The data scattered on the chart represents each task within a stage against the number of days they are in that stage. Let’s take the example below.

This WIP chart shows there are three tasks in the Development stage, with two of them being in Development for 2 days and one for 4 days. Two tasks are in Code Review stage for 2 days and so on. The dotted horizontal lines that run across the chart indicate the percentage of tasks that have been completed historically. For example, if a task has climbed past the 50th percentile, this means that it’s already taking more time in your process than 50% of your past tasks. The higher a task is plotted in the chart, the longer it is staying in progress.

You can use these percentiles as guides to spot whether a task is taking longer than you’d expect. For some, a task crossing the 50th percentile may be a cause for concern. It would depend on your team’s threshold. The WIP aging chart also depends on the date range you run the data on. So the basis of historical data will change. There are digital Kanban tools that have this report built-in but you can also do it manually through a spreadsheet.

WIP charts are useful for planning your team’s capacity, especially when stakeholders ask you to forecast future projects. In our chart example above, we could say that there’s a 50% chance that the team can deliver a task within 7 days and a 70% chance they can finish it in 12 days. The more tasks you work on, the more reliable your data will be.

Keep your WIP age young

To maintain a stable and predictable flow, you must not only limit the number of tasks you work on but also keep your WIP age low. A good way to prevent your WIP from aging is to introduce due dates on your task. If your team commits to delivering a task within 10 days, set a due date 10 days from when the task is started. You can set an indicator in your task cards when it’s nearing its due date so the team can do what they need to follow through their commitment.

You can also have a policy that uses percentiles to decide if a task needs to be expedited. For example, if a task has passed the 50th percentile, it will be converted to a high priority or expedite class of service where the team must ensure this task goes out first. This prevents your task from aging much longer than it already has.

These tips are a good start to prevent delays in your process. Start monitoring your WIP age and create a more stable and predictable flow for your team.