Using Input / Output charts

These are not very widely used, but are one of my favourite charts for helping to manage flow. I find it quite simple as well, which once you finish this article I hope you also find it equally simple and useful.

When managing flow you often want to make sure you team are not taking in more work they can handle, plus you also want to make sure they don’t “starve” for work. Continually looking for balance can often seem difficult, but using this chart you can help achieve the balance your looking for.

Here’s a look at a net flow chart:

Essentially, the green points above the line mean that for that week you’ve gotten more items done that what you’ve started. The red points below the line represent weeks that you’ve started more items than you’ve completed. Those weeks that don’t have a line in them (with a zero) are weeks where you’ve balanced input and output (well done!).

Where you see build ups of several weeks of the one colour, that’s usually a warning sign that you’re flow is out of balance.

You can see in the early part of this chart there is a lot of red. That indicates that WiP is increasing and is often an indicator that you need to start to choke the input to your system or it will be overwhelmed. However, there is often an exception to this where teams are bootstrapping / starting out – you want to start to pull work into the system and it will take some time before the first item flows out.

Alternatively, if you get a number of weeks of all green it means that you’re team are finishing a more work than they started. This is an indicator that you need to get out and start some more work. In the event that you have an upstream, you may have a lead time before that work comes to your system. It’s important to see these signals early and can respond to it.

In first diagram above, you can see in the middle there were a period of time where it was back and forth. Then towards the end you can see balance starting to be achieved. This is an important part of how you use this chart – often with a large board and different work items types / classes of service, it’s hard to see important details of this without the data representation. I hope that you can now you can see the value in this chart and can try and use it.

It’s freely available here if you wanted to download it:

http://bit.ly/SimResources

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