User blog comment:Dragonjet/KanColle English DB/@comment-24835439-20140419151825/@comment-119.56.124.52-20140420103358

"That thing happens very few times in comparison with how many sorties you (and other people) do, so they wouldn't really affect much the drop rate. This will just make everything more complicated."

It's not that complicated really, a quick check at the statistics page will tell you all you need to know. You need at least one free space for ships and 4 free spaces for equipment to get any drops.