Do Miss Chances Stack?

[Kref]

Mirror image won't save against missiles, except of those which were shot at close range or with high precission. Missiles shoot in a ground. For example, if an arrow hitted a square and there is a size 2 infantry on it, there is 1/3 chance that an arrow strike would apply to that infantry; if there are three such infantries on that square, then arrow would apply on one of them for sure, of couse then air shield - luck - body ethereal would play.
I wonder about next thing: let's consider that an ethereal creature was attacked 4 times (for example), and one of the attacks was applied with unsucsesful chance of etherealness. What attack bonus due to swarming would apply to fifth attack on that creature? 4*4 = 16 or 1*4 = 4?