Comment by arjie

This is a classic problem when people try to find "the current price" of something. A typical error is to take an average of the current rentals currently on the market and describe that as the average rental cost somewhere. Usually the book is so thin that a few places being taken off the market will shift the price a lot while most people can be paying something like half of that and every rental that lists for less than the clearing price is acquired so rapidly that any sampling method will reliably miss it.