yet I don't see any huge drops around December 2015 (between 2015-11-02 and 2015-11-09 it went from $501 to $297 but back then this was still considered "normal" I suppose).
it is all about the percentage-wise size of any movement not the absolute size. from $501 to $297 is a 40% drop so it can not be considered "normal" really even in bitcoin market. so if you wanted to compare it to this month's drop it is half that size.
in any case i don't think we can make this kind of comparison on small levels. we can compare them with a bigger perspective meaning expecting the big hyped up rise 1-2 months prior to the halving, a mini bubble by the time of halving, its burst right on halving and slow rise 1 month after it.