The San Jose Public Library wants its books back. And its CDs and DVDs. Taken altogether, library patrons are holding onto or have damaged 97,000 items and owe the city $6.8 million in fines and fees. The situation is so out of control that about 40 percent of the city’s library cardholders can no longer borrow anything until they return their library holdings and pay what they owe. For a library, this is a DEFCON moment. Maybe not DEFCON 1, but at least DEFCON 3.

What can San Jose do? City councilmember Pierluigi Oliverio has suggested a limited-time amnesty on fines for overdue materials. “If you bring those items back, that’s worth a lot of money just in that inventory of items,” he said earlier this month. In other words, in return for its patrons doing what they’re supposed to do, the library will let bygones be bygones. What’s a little fine between friends, after all?

Over the years, libraries have fined patrons for not bringing back books and offered no-questions-asked return periods. They’ve published the names of book scofflaws in local newspapers. They’ve paid personal calls on people who hold onto books past their due dates, and even sicced the police on particularly recalcitrant readers. And they still don’t really know how to get their books back.

“Librarians have been playing with this issue for a century and a half, and there is little consensus,” says Wayne Wiegand, author of Part of Our Lives: A People’s History of the American Public Library.

One thing’s for sure: Taxpayers often bristle at amnesties, seeing them as gimmes for slacker citizens. And so it is in San Jose, where more than a few were quick to complain. “As a property owner, I’m sick and tired [of] subsidizing the libraries and having to subsidize malfeasance,” one person said at a city government meeting held earlier this month. An amnesty, he added, “enables lack of personal responsibility.” Online commenters weren’t much more supportive. “Once again, irresponsible people getting all the breaks,” one said over at the San Jose News.

Maybe. But no one’s actually proven that fines work. “Our first rule of thumb is we are providing materials with taxpayer funds,” says Julie Todaro, the incoming president of the American Library Association. But, she’s quick to add, “A lot of people will tell you higher fines aren’t a detriment to returns. It is a detriment to people using the library. Period.”

San Jose’s problems began when it raised fines in 2010, from 25 cents to 50 cents a day. Other area libraries charge less. San Francisco dings late borrowers 10 cents for every day late, with a hard stop at $5. The San Mateo County Library, where borrowers from wealthy Atherton check out books, charges 25 cents a day for adult books, up to $8, and 15 cents a day for children’s books, up to $3.90. Exclusive Mountain View is also at 25 cents, and allows borrowers to keep books for four weeks.

San Jose not only charges borrowers more money for late returns; it has a three- week borrowing window, and allows fees to accrue until they reach $20. At the same time, it’s likely a greater percentage of city borrowers are having a harder time paying the money. Children owe $1 million of the unpaid fines. And many of these kids need the library. While located in wealthy Silicon Valley, San Jose contains significant pockets of poverty, with 47 percent of the city’s school public school district’s students eligible for free or reduced lunch.

In Wiegand’s view, library fines are vestigial, a leftover from 200 years ago, when books were highly valuable items, and few could afford to purchase them. Handing over a book for a limited period of time involved a significant financial risk for the lender, and a fine protected that investment.

But even back when, a fine couldn’t guarantee a library would get its goods back. Even George Washington neglected to return The Law of Nations by Emer de Vattel and a volume of debates from the English Parliament to the elites-only New York Society Library.

The New York Society Library needed to wait until 2010, when the New York Daily News outed the founding father, to recover its property. Embarrassed employees of the Mount Vernon historic site saw the article and tracked the missing items down. In return, the New York Society Library gratefully waived the $300,000 in overdue fines. (Alexander Hamilton and Aaron Burr agreed on one thing, by the way. New York Society Records showed they returned borrowed books regularly.)

Fines had another thing in their favor: They could double as a source of revenue. During the Great Depression, the Cleveland Public Library’s budget shriveled by 40 percent. So it began promoting “overdue weeks,” in which flush patrons were encouraged to hold on to their borrowed books past their due date and pay the fine, an effort to bolster the library’s bottom line.

A large number of California municipalities turned to fines to get by in the wake of anti-tax measure Proposition 13. According to archivist Cody White, who wrote an award-winning paper on the subject, within two years of the tax-cutting initiative’s passage in 1978, 40 percent of the state’s libraries had either raised or added fees as a way to bring in desperately needed revenue. Some systems even began to charge nonresidents for the privilege of getting a card.

And when that wasn’t enough, many California libraries turned to collection agencies. This was so successful that it’s now a widespread practice. There’s even a collection agency—Unique Management Services—that specializes in library accounts, and handles the most recalcitrant of borrowers for 1,400 library systems in the United States, Canada, and the United Kingdom.

Unique uses a method it calls the Gentle Nudge, which basically means that no, it won’t call you multiple times a day to ask where the books are. But it doesn’t play all that nice, either. Instead, the agency reports malfeasant patrons to credit bureaus if they don’t return the missing materials and pay up. It’s a potent threat. The Madison, Wisconsin Public Library, for example, reports that in the 10 years since it brought in Unique, it paid the company slightly more than $120,000 and, in return, got back just under $1 million in overdue fines and missing materials. Few people, after all, want to pay higher interest rates on loans ranging from mortgages to credit cards because of a library book.

Not surprisingly, patrons aren’t fans. About a decade ago, a New York City rabbi sued Unique after discovering his credit record was damaged when he failed to return several CDs to a library. Librarians don’t always like firms like Unique, either; in 2001, San Francisco politicians dinged a proposal to turn seriously overdue borrowers to a collection agency after librarians complained. Not only did they think it unfair to patrons; they insisted it was their job to rustle up the lost books.

On the other hand, a collection agency is probably preferable to the police. Arrests aren’t unheard of for book hoarders, but nothing is more absurd than the time in 2012 when police in Charlton, Massachusetts, paid a call on the family of a 5-year-old girl who hadn’t returned How to Tie My Shoes and Eloise’s Birthday. Her dad also owed money for an audiobook. National ridicule ensued, but the library said the visit inspired other borrowers to return their books. “We’ve gotten quite a bit back,” a library spokeswoman told CNN. “Even some things that weren’t overdue!” Other times, the involvement of public officials can at least be amusing. In the 1980s, the notoriously eccentric Baltimore mayor William Schaefer called surprised patrons, and said, “Hey, this is the mayor. How about returning your library books?”

Some systems try their own gentle nudges. The Phoenix Public Library, for example, will forgive fines for teenagers enrolled in summer reading programs who write book reviews of what they’re reading. In Nashville, the public library has offered a Food for Fines exchange, knocking $1 off an outstanding bill for every packaged food item a debtor owes donates.

But others swear by limited-time amnesties. They were popular during the Great Depression, when libraries couldn’t afford to replace lost materials and patrons couldn’t afford to pay the fines. They remain popular today—Chicago has offered two amnesties over the past five years, recovering more than 120,000 items. Getting decades-old overdue books isn’t unusual during amnesties. A 1983 Philadelphia amnesty netted $1.5 million worth of books and other library property, including a book originally checked out in March of 1922.

In fact, amnesties have a lot of things going for them. The limited-time offer ensures media attention, so locals will hear about it. They’re also not punitive. That’s important to librarians, who love books, want their materials back, and want their patrons visiting frequently. If fines work, they’ll go along, but if an amnesty works, they’ll take that, too.

Meanwhile, back in San Jose, the library announced plans to debut an improved texting system to notify borrowers when their books are due. Maybe some really naggy emojis will do the trick?