In terms of sibling effects, they could be large drains. Imagine a sibling who never bothers to buy their own socks but just unconsciously takes one sock too many once in a while. If there's 2 siblings, now the responsible one must buy twice as much socks as they should (because of the hidden drain). Such people would simply show up as rare-purchasers in my survey, and there are quite a few such people. Ones lost in a dryer may be de facto permanently gone: even if you pull the units out a decade later and find them, do you even want to wear them anymore? And what does one do with a mismatched sock? If its mate doesn't show up in a few months, you might toss it or use it for something else entirely, and then should the mate reappear later, now it's a mismatch as well... I certainly don't lose 8 pairs of socks a year, but then, I don't spend $200+ a month on groceries either.