Our survey says… uncovering the real numbers behind flow efficiency

Nick Brown
ASOS Tech Blog
Published in
9 min readJul 26, 2023


Flow Efficiency is a metric that is lauded as being a true measure of agility yet it has never had any clear data supporting it, until now. This blog looks at over 60 teams here in ASOS and what numbers they see from a flow efficiency perspective…

A mockup of a family fortunes scoreboard for flow efficiency

Not too long ago, I risked the wrath of the lean-agile world by documenting the many flaws of flow efficiency. It certainly got plenty of engagement — as it currently is my second most read article on Medium. On the whole it seemed to get mostly positive engagement (minus a few rude replies on LinkedIn!) which does make me question why it still gets traction through things like the flow framework and Scaled Agile Framework (SAFe). I put it down to something akin to this:

A comic of mocking a consutlancy changing their mind on selling SAFe
Source: No more SAFe

For those who missed the last post and are wondering what it is, flow efficiency is an adaptation of a metric from the lean world known as process efficiency. This is where, for a particular work item, we measure the percentage of active time — i.e., time spent actually working on the item against the total time (active time + waiting time) that it took to for the item to complete.

For example, if we were to take a team’s Kanban board, it may look something like this:

An example kanban board
Source: Flow Efficiency: Powering the Current of Your Work

Flow efficiency is therefore calculated like so:

An explanation of the flow efficiency calculation of active time divided by total time multiplied by 100

One of my main issues with Flow Efficiency is the way it is lauded as the ‘thing’ to measure. There are plenty of anecdotal references to it, yet zero evidence and/or data to back up the claims. Here’s some of the top results on Google:

None of these statements have any data to support the claims they make. Rather than bemoan this further, I thought, in line with the previous blog on Monte Carlo forecasting accuracy and with the abundance of teams we have in ASOS Tech, let’s actually look at what the data says…

Gathering data

At ASOS, I am very fortunate as a coach that those before me such as Helen Meek, Duncan Walker and Ian Davies, all invested time in educating teams about agility and flow. When randomly selecting teams for this blog, I found that none of the teams were missing “queues” in their workflow, which is often the initial stumbling block for measuring flow efficiency.

Flow Efficiency is one of the many metrics we have available to our ASOS Tech teams, to use when it comes to measuring their flow of work and as an objective lens in their efforts towards continuous improvement. Teams choose a given time period and select which steps in their workflow are their ‘work’ states (i.e. when work on an item is actually taking place):

An animation showing how teams configure their flow efficiency metric

Once they have done this, a chart will then plot the Flow Efficiency for each respective item against the completed date, as well as showing the average for all the completed items in that period. The chart uses a coloured scale to highlight those items with the lowest flow efficiency (in orange) through to those with the highest (in blue):

An example of a flow efficiency chart showing 29% for a completed item

For this article, I did this process for 63 teams, playing around with the date slicer for periods over the last twelve months and finding the lowest and highest average flow efficiency values for a given period:

An animation showing the date range showing different flow efficiency calculations

This was then recorded in my dataset like so:

A table showing the minimum and maximum flow efficiency measures for a team

All teams use a blend of different practices and frameworks — some use Scrum/ScrumBut, others use more Kanban/continuous flow or blend these with things like eXtreme Programming. Some teams are working on things you will see on the front-end/customer facing parts of the journey (e.g. Saved Items), others back-end system (e.g. tools we use for stock management and fulfilment).

Now that I’ve explained the data capture process — let’s look at the results!

Our survey says…

With so many teams to visualize, it’s difficult to find a way to show this that satisfies all. I went with a dumbbell chart as this allows us to show the variance in lowest-highest flow efficiency value per team and the average across all teams:

A summary dumbbell chart of the results showing a range of 9–68%

Some key findings being:

  • We actually now have concrete data around flow efficiency! We can see that with this study flow efficiency values from 9–68% have been recorded
  • The average flow efficiency is 35%
  • Flow efficiency has variability — any time you hear someone say they have seen flow efficiency values typically of n% (i.e. a single number), treat this with caution/scepticism as it should always be communicated as a range. We can see that all teams had variation in their values, with 38% of the teams in this data (25 of 63 teams) actually having a flow efficiency difference of >10%
  • If we were to take some of those original quotes and categorised our flow efficiency based on what is ‘typically’ seen in to groups of Low (<5%), Medium (5–15%), High (15–40%) and Very High (>40%) then the teams would look something like this:
A chart showing the distribution of results

The problem with this is, whilst we do everything we can to reduce dependencies on teams and leverage microservices, there is no way nearly all teams have either high or very high flow efficiency.

I believe a better categorisation that we should move to would be — Low (<20%), Medium (20–40%), High (40–60%) and Very High (>60%), as this would look like:

A chart showing an updated distribution of the results

But, but…these numbers are too high?!

Perhaps you might be reading this and have your own experiences and/or share the same views as those sources referenced at the beginning of the blog. There is no way I can disagree with your lived experience but I do think that when talking about numbers people need to be prepared to bring more to the conversation than anecdotal reference points. Are these numbers a reflection of the “true” flow efficiency of those items? Definitely not! There is all the nuances of work items not being updated in real time, work being in active states on evenings/weekends when it clearly isn’t being worked on (I hope!), work actually being blocked but not marked as blocked etc. — all of which I explained in the previous article.

Let’s take a second and look at what it would mean practically if you wanted to get a more ‘accurate’ flow efficiency number. Assume a team has a workflow like so:

An example kanban board

If we take for example, 30 work items that have been completed by this team in a one month period. We assume that 60% of those items went through all columns (7 transitions) and the remaining 40% skip some columns (2 to 6 transitions) — allowing for some variability in how items move through our workflow:

An example table of data showing column transitions

Then we assume that, like all teams at ASOS (or teams using tools like Azure DevOps or Jira), they comment on items. This could be to let people know something has progressed, clarify part of the acceptance criteria, ask a question, etc. Let’s say that this can happen anywhere from 0–4 times per item:

An example table of data showing column transitions and comment count

Not only that but we also mark an item when it is blocked and also then unblocked:

An example table of data showing column transitions, comment count, times blocked and unblocked
Note: randomised using Excel

Now, if we just look at that alone, that means 348 updates to work items in a one month period. If we then wanted to add in when work is waiting, we would need to account for a few (2) or many (6 — conservatively!) times an item is waiting, as well as adding a comment sometimes (but not all the time) so that people know the reason why it is waiting:

An example table of data showing column transitions, comment count, times blocked and unblocked, wait time and waiting reason
Random values again calculated via Excel :)

We can already see that with these conservative guesses we’re adding nearly 200 more updates to just 30 work items. Once you start to do this at scale, whether that be for more items and/or more teams as well as over a longer period, you can see just how much additional work this means for teams in interacting with their tool of choice. Combine this with the costs of context switching (i.e. moving out of being ‘in the work’ to log into the tool that you are ‘waiting’) and you can see why tracking flow efficiency to more accuracy is a fools errand.


My hope is that we can now start to have a proper conversation around what ‘typical’ flow efficiency numbers we see. Whether it be what ‘typical’ values you see or what a ‘high’ flow efficiency looks like. To my knowledge this is the first attempt at something like this in our industry… and it should not be the last! In addition to this, I wanted to demonstrate what it would truly mean if you wanted a team to place more focus on getting an ‘accurate’ flow efficiency value.

For those wondering if it has changed my opinion on flow efficiency, as you can probably tell it has not. What I would say is that I have cooled a little on flaw #1 of teams not modelling queues in their workflow, given nearly all these teams had multiple queue states modelled (after good training/coaching). I still stand by the other flaws that come with it and now I hope folks who are familiarising themselves with it have this information as a common reference point when determining its appropriateness for them and their context.

What are the alternatives? Certainly Work Item Age would be a good starting point, as items aging at a rate greater than your historical cycle time might allude to an inefficient way of working. Another approach could also be looking at blocked work metrics and insights those bring.

What are your thoughts on the findings? Surprised? Sceptical?
Let me know in the replies what you think…

About Me

I’m Nick, one of our Agile Coaches at ASOS. I help guide individuals, teams and platforms to improve their ways of working in a framework agnostic manner. Outside of work, my new born son keeps me on my toes agility wise, here’s a recent photo of him and my wife Nisha (to my left) meeting the team…

An image of the author with his wife and the rest of the agile coaches at ASOS