I just got an email from the Free Library of Philadelphia announcing that they no longer charge fines for material returned past the due date. The announcement, reproduced on their blog contained the following sentence:
Overdue fines keep many patrons from enjoying all the Library has to offer, and evidence shows they have no significant impact on the return rate of checked-out materials.
That surprises me. I certainly expect to keep items out longer than I used to. So in a sense my "return rate" will go down, get worse, if "rate" is conceived as items per number of days out. On the other hand it seems possible that "return rate" will go up, get better, in the sense that customers will no longer see the overdue fines as a reason not to return overdue items at all, working as a sunk cost to apply to the charge for a lost item. But this seems like a rather far-fetched reading of the message, as naturally the original theory of overdue fines was that patrons would try to return books on time to avoid the fines, not that they would prefer to pay larger fines when returning books.
Do fines affect on-time and/or eventual return rates?