I started noticing something that left me wondering a bit. My estimate is that the average paper (for example submitted to physical review journals, contains of the order of 50 citations). But if the average paper cites 50 other papers, then each paper should also receive 50 citations on average.
This is definitely not my track record. One could argue that cited papers are dominated by a few rare events (very important papers with thousands of citations), but by the very definition of an impact factor this cannot be the case, (unless one considers books, but I would assume they comprise max 20% of the citations): only top journals as nature reach an impact factor of this order, but these are far from the only papers cited. Many of them are other physical reviews, with an impact factor of order 3.
So that leaves me wondering, where are the missing citations going? Is it just a matter of delay, or is there a flaw in my logic?