Well, for that matter it also depends on what you can do about it, and I have no idea how we would go about preventing Yellowstone from erupting.

I remember a proposal about cooling down Yellowstone by putting a lake on top of it.

If you spent more money you can ram carbon nanofiber rods deep into the ground. If the rod is thick enough the lave shouldn't do much damage to it and it can very effectively transport temperature to the top. Maybe you get even electricity as a bonus for cooling down Yellowstone so the project would pay for itself.