Trigger when all living players are in an area?

[TacoTuesday 1]

I am trying to figure out how to make a trigger go off when all living player units are in the trigger area. How would I go about this? I imagine its something to do with

this; (player in thislist)

but I am not sure. From what I understand that would fire off when any player enters that area, not all alive players.

[warlock89 10]

Group the trigger with the unit group and set the trigger to activate once when present, and under activation you put "Whole group".

[cuel 25]

COOP? Try this.

{isPlayer _x} count thisList == count playableUnits