Applying the toolThe IOWA Number can be used in the "Gather Data" stage of a Retrospective with the question: "How do you feel about your team members?" This does require a certain level of trust within the team to work properly, and be clear that the tool isn't meant to highlight people as problems, but much rather to help the team find itself properly. There is no score that's inherently good or bad, just some scores that will lead to further conversation down the road.
Most importantly, only apply the tool when you have a feeling that there are some outliers, as the tool is merely intended to open up a conversation on becoming better at collaborating!
Extremely low scoresIn some, rare cases the team will feel that a person's absence will actually have a positive effect on outcome.
The most notable case of this happening is usually when said person is lacking so much knowledge that their questions disrupt the others' flow of work. A good way to strengthen the team would be to put delivery work a bit on the backburner and work intensely to bring the person back to speed.
Another common case would be that said person doesn't really understand the impact of their own way of working on the team, often due to being unfamiliar with others' self-organized ways of working.
In any case, team members with extremely low IOWA score need the team's support to rise to higher levels and the team should have an open conversation which behaviours are reducing IOWA score and which behaviours would increase it.
Moderate scoresAnything between 3 and 7 is usual. There's not much to discuss, unless there are tendencies towards an extreme. But since IOWA numbers are nothing more than a snapshot in time, it would be better to use the extreme value right away, as it doesn't make sense to defer a conversation.
Extremely high scoresThere's no way to sugar-coat it, high IOWA scores are a risk, potentially even a threat to the team's sustainability!
People typically do not choose to have high IOWA score, they receive that score because they have superior understanding of a subject matter and a strong drive for action. Usually, they feel they are helping the team and the organization by working this way, and in fact - when it comes to getting stuff done, they help a lot.
Unfortunately, all of their help us unsustainable, as the team immediately falters when they aren't available and if for some reason, they should be out (e.g. sickness, family issues etc.) their absence could bring the entire team and whatever the team was working on to a standstill or collapse.
As I wrote in my book, "Extreme Agility", my suggested course of action would be to relieve the person from the responsibility of doing whatever they do so well and instead coach and support the rest of the team in this. It should be exceedingly clear that they aren't taken out of the delivering function because anything is wrong with them, but because they are needed as multiplicators in order to grow the team.
ConclusionIOWA Numbers are a conversation starter when the team is on uneven footing. It's not intended to judge or condemn the work or contribution of any individual, much rather it is intended to bring people to a more equal footing in order to increase the team's sustainability.
In some cases, it may even be worthwhile to create IOWA Numbers for people in the team's close vicintity, such as traditional line managers. If this is done, be sure to include them in the Retrospective (which is rather unusual).