There are three kinds of participant: those who must be there, those who can be there, and those who don't need to be there.
The problem is that we treat all three the same. And so we end up with eight people in a session that needed four — which costs more, decides less, and leaves half the room wondering why they came.
Why does the list always grow?
Because leaving someone off feels like a statement, and adding them feels like nothing.
Every name added has a cost that shows up later and a social cost that shows up immediately. So the immediate cost wins, every time, and the list grows by one or two people per revision until the room is too big to decide anything.
Nobody ever pushed back on an invitation list for being too long. That's the whole problem.
The five-minute exercise
Before you send the next invitation, sort every name into one of three groups.
Must be there. Invite them. Without this person you cannot reach the outcome — they hold the decision, the information, or the accountability.
Can be there. Useful input, but not decisive. Consider whether they could join part of the session instead of all of it.
Doesn't need to be there. Send a summary if it's relevant. Or commit to telling them about any action points that involve them, if any come up.
That's it. It takes five minutes and it's the highest-leverage five minutes in the whole design.
What size are you aiming for?
Small enough that everybody in the room has a reason to speak.
If you can't say out loud why a specific person is there, they're in the second or third group. That's not a judgement about them — it's a judgement about this session.
Doesn't this exclude people?
It's the opposite, if you do the third group properly.
The failure mode isn't the small room. It's the small room plus silence afterwards — people who weren't invited and never heard what happened. That's exclusion. A short summary to the people who didn't need to be there costs you ten minutes and removes the entire objection.
The "can be there" group is worth designing for too. Bringing someone in for a 45-minute slot where their input matters is better than having them sit through six hours to contribute twice.
What you get back
The people who are there feel more relevant, because they are. The discussion gets sharper, because everyone in the room has a stake in it. And decisions get made, because four people can decide something that eight people will only discuss.
A shorter list is not a less inclusive meeting. It's usually a more honest one.