01252 727270

Log in to AOD Connect

Does team size matter?

by Professor Michael West


Updated 7 March 2019

(originally posted 3 July 2018)

When it comes to team meetings, Amazon boss Jeff Bezos swears by his famous ‘two-pizza’ rule – limiting the number of people involved to no more than can be fed with two pizzas.

But what does the research say about the optimum size for a healthcare team? And how can we overcome some of the challenges of working in very large teams? Do team assessment tools retain their validity as teams gets larger? And are they still accurate in highlighting strengths and development needs in teams?

The optimum size for a healthcare team

International research suggests that a team should have the minimum number of people needed to get the job done and no larger. That implies efficiency and ensures there are not extra people on teams who are underemployed and dissatisfied with their contribution.

“our data from the NHS over the last 30 years suggest that ideally teams should not exceed 8 to 12”

Beyond that, our data from the NHS over the last 30 years suggest that ideally teams should not exceed 8 to 12 (Borrill et al., 2001; West, 2012). This is because as teams increase in size beyond this number, team members are less clear about team objectives, find information sharing more difficult, interact less and feel they have less influence over decision-making. Moreover, they perceive less support for their ideas for new and improved ways of doing things and indicate that conflict in their teams is higher.

Overcoming the challenges of working in very large teams

The larger the grouping the more likely the team is to fail through ‘process loss’. For example, once teams go above eight or nine members, they will experience much greater strains on effective communication. This is because the number of communication channels increases quickly with the addition of each new team member until it becomes very difficult for team members to share information effectively. And it is difficult to create close, shared understanding when we have large numbers of team members and therefore more difficult to work effectively together.

One way around this is to have detailed protocols for how the team should work together so that mutual understanding and human closeness is less critical. This is how cockpit crews work in the planes that fly us to our holiday and business destinations – creating very fixed rules and processes for how to work together. Even so, such protocols cannot entirely prevent misunderstandings, especially in crisis situations or when unanticipated problems arise.

As teams get larger, we can encourage effective team working by ensuring clarity about each other’s roles and coaching new members to ensure they too understand the roles of others on the team (Lyuobvnikova et al., 2015).

Creating sub-groups within a team

Another solution is to create sub-teams when teams get too large. So, in a team of (let us say) 20 people, we might break the team task up into three or four areas with a sub-team primarily responsible for each.

One sees this in some sports teams, such as rugby, where the team of 15 is effectively broken into two groups – the six backs and eight forwards who take on quite different roles. They are aided by a link player, the scrum half, who acts as an intermediary between the two sets of players. When teams are divided into sub-teams, it is vital that these sub-teams work interdependently and ensure effective communication and coordination to enable overall team effectiveness.

Team reflection time is important, especially to large teams

Also vital is for large teams to increase the time they devote to ‘reflexivity’, reflecting on what they are trying to achieve, clarifying objectives, reviewing how they are working and what they need to change, and making changes accordingly (Schippers et al., 2012).

Such reflexivity helps teams correct and refocus on a regular basis. It also provides an opportunity to consider the creation of more focused sub-teams when appropriate.

Taking time out to review objectives, strategies and processes is a powerful aid to team learning and to health care team effectiveness and is associated with higher productivity and innovation, regardless of team size. Our research shows it is even more important for larger teams but is not widely practised.

Do assessments lose their validity as team size reaches 15 or more?

Team assessments do not lose their validity but will reveal some of the problems of large team working if the instruments are reliable and valid.

We have designed the AOD tools, including the Affina Team Journey, to ensure that large team size does not undermine the value of the diagnostic process.

The AOD tools offer an understanding of how teams vary in relation to average scores on key dimensions, but what is particularly valuable is that they provide an indication of the extent of agreement (and therefore disagreement) among team members about how they see the team working. It is likely that larger teams will be characterised by more disagreement, thereby offering the opportunity for discussions about how to develop better mutual understanding – sometimes called shared mental models.

Two pizzas?

Maybe the two-pizza rule works for a highly automated and algorithmic organisation like Amazon but the NHS is a more complex system.

Looking after the health and well-being of NHS staff is key to looking after the health and well-being of our population. We have clear evidence that NHS staff working in well-functioning teams are significantly less stressed because they have better social support, clearer roles and are buffered from some of the wider organisational stresses around them.

I don’t come across many health care teams where the staff have time to eat pizzas, let alone order them during their shift. So the two-pizzas rule has its merits but ensuring effective team working, irrespective of team size, is better.



Borrill, C.S., Carletta, J., Carter, A.J., Dawson, J.F., Garrod, S., Rees, A., Richards, A., Shapiro, D. & West, M.A. (2001). The effectiveness of health care teams in the National Health Service. Aston Centre for Health Service Organisational Research, University of Aston, Human Communications Research Centre, Universities of Glasgow and Edinburgh, Psychological Therapies Research Centre, University of Leeds.

West, M.A. (2012), Effective Teamwork: Practical Lessons from Organizational Research, Oxford, Blackwell Publishing, 3rd Edition.

24-Karat or fool’s gold?: Consequences of real team and co-acting group membership in healthcare organizations Lyuobvnikova, J., West, M., Dawson, J. & Carter, M. European Journal of Work and Organizational Psychology. 24, 6,p. 929-950 22 p, 2015

Schippers, M. C., West, M. A., & Dawson, J. F. (2015). Team reflexivity and innovation: The moderating role of team context. Journal of Management. 41, 769–788. DOI: 10.1177/0149206312441210

Individual Team Development

Improve team effectiveness through in-depth direct support of selected teams
Read More

Affina Team Journey

Improve performance across your organisation by giving your team leaders a practical 'tool-kit' they will value and enjoy
Read More

Training for Team Facilitators

Take your work with teams to the next level as an accredited ATPI facilitator
Read More

Sign up to our newsletter