Big Cat
Isn't that the point of informal complaints? To stop the harassment before it needs formal action? You have a word, harasser apologises and starts behaving, job done with no paperwork! From these stats, maybe it's working! Or am I being a bit hopeful there?
I think this is part of it but, significantly, until VERY recently the perpetrator was often allowed to judge his/her own case. The rules required complaints to be elevated through the management / command chain and if the perpetrator was in that chain, it put a lot of victims off. The rules have changed, allowing one to bypass management if they are the problem.
In such a robust walk of life these cases are always difficult. The last one I had to deal with, a young NCO had been over-suggestive to two older female civvies. One complained, the other admitted she loved it. A quiet word followed by an apology fixed it, as to proceed further would have been a waste of time. Common sense, now overtaken by PC.