Bestseller lists have long been powerful marketing tools for the industry. In short, they sell books. But they have proliferated, with more lists that group books according to different metrics, and industry insiders are wondering whether they wield as much power as they used to. When nearly any title can be called a bestseller, does becoming a bestseller still matter?

Though insiders we spoke with agreed unanimously that the term “bestseller” still means something to readers, they disagreed on how lists affect the market and what actually defines a bestseller.

Historically, bestseller lists were broken down along two major lines: format and category. The largest groupings were nonfiction and fiction. Those groups were then broken down by the three major print formats: hardcover, trade paperback, and mass market paperback. The introduction of the fourth format—e-books—disrupted the way bestseller lists are compiled, as it did many other parts of the industry. Because e-books are predominantly sold online and not in stores, their sales can’t be tracked in the same way that print sales are: by collecting data from physical retailers.

Further complicating the bestseller list landscape was Amazon’s introduction of multiple bestseller lists. The e-tailer, which tracks sales of its titles in real time, publishes a wealth of lists, broken down by format and also by multiple subcategories. There are “overall” print and Kindle bestsellers on the site, but also numerous subcategories like “Crafts, Hobbies & Home,” “Humor & Entertainment,” and “Law.”

The sources of the data on which the lists are based also complicate their interpretation. The New York Times famously pulls data for its lists from a select and secret sample of retailers, and Amazon, while reporting its print sales, does not, for the most part, disclose sales of e-books. The lists that are arguably the most transparent, like PW’s, rely on NPD BookScan’s point-of-sale data, which tracks 80%–85% of print sales in the country but doesn’t include data on e-book sales. Other news outlets, such as the Wall Street Journal and USA Today, run their own lists, and organizations like the American Booksellers Association produces multiple lists, including an overall list of bestsellers in ABA bookstores and regional lists.

The sheer number of lists and Amazon’s decision not to widely share its e-book sales figures (despite the fact that BookScan has for years asked the company to take part in its sales aggregation program) means that there is not a true national bestseller list that can definitively identify what the top-selling books are across all formats in a particular week. As a result, there’s some confusion about what the designation “bestseller” really means.

“Even when it comes to ‘national bestseller,’ it seems that we don’t have a consensus [about the meaning of the term],” said one agent, who asked to remain anonymous. “Not that long ago, it meant a lot if you said a book was a bestseller. Why? Because a select number of books earned that accolade, and we all understood and agreed what it meant.” Now, he said, he worries that the multiplicity of lists has “watered down” the designation.

“Every publisher must make a decision on when to refer to a book as a bestseller,” said Bill Wolfsthal, executive v-p of sales and marketing at Skyhorse Publishing. “Was it a bestseller on Amazon for a day? Is it a bestseller if it makes a bestseller list for independent bookstores? In those decisions, good judgement and common sense rules the day. No publisher wants to mislead a reader, but we are all fighting to get attention for our books.”

Whether the bestseller tag even really drums up attention is also a point of debate. “As long as it has an XYZ in front of it—as in New York Times bestseller, USA Today bestseller, or Wall Street Journal bestseller, I do think it carries weight with the reader,” agent Kristen Nelson said. “If it just says ‘bestselling author,’ I do think readers tend to perceive the moniker with some skepticism.”

Ironically for booksellers, titles dubbed bestsellers aren’t necessarily popular with customers. Vivien Jennings, who owns Rainy Day Books in Fairway, Kans., said that bestseller lists “draw attention” to books, but that attention doesn’t necessarily translate into sales. Anmiryan Budner, a bookseller at Main Point Books in Wayne, Pa., said the real sales boosters are good reviews; coverage in high-profile media such as NPR, 60 Minutes, and morning TV shows; and word-of-mouth.

The Times list, for its part, has been the subject of some controversy in the industry. Historically it has been seen as the list with the most caché. But the secrecy of the formula the paper uses to compile its list has long created frustrations in the industry, with complaints over the years that it does not offer an accurate picture of what’s actually selling.

About half of those we spoke to referred to the Times’ list as the “premier” list, the “gold standard,” and the “crown jewel.” Others said it was not the kingmaker it once was.

“I would say that the Times in general, like any media outlet in digital, print, and broadcast, does not have the same impact in terms of driving book sales that it once did,” said Knopf’s Paul Bogaards. Nonetheless, he said, publishers still rely heavily on the name: “Clearly, publishers still believe in visibly branding their books with ‘New York Times’ or ‘national bestseller.’ Have a look at the covers of some titles in the marketplace right now. [Many] are festooned with the bestseller copy.”

Carol Fitzgerald, president of the Book Report Network, admitted that she still believes “everybody wants the Times list more than anything else.” Despite this, she prefers “lists that are actually based in sales; no algorithms, just sales.” She added: “That’s really what a bestseller is, isn’t it? How it’s sold.”

While the proliferation of bestseller lists is a worry for some, reducing the number does not seem to be the preferred response. Many of the sources we contacted said they are upset that the Times cut a number of category bestseller lists. “Eliminating a bestseller list in a strong and previously established category—as happened for YA and graphic novels, for example—feels like a step in the wrong direction,” agent Laura Rennert said. A fellow agent, Barbara Poelle, said: “I feel like there isn’t a week that goes by where I don’t lament, curse, howl over the loss of the mass market and YA e-book lists in the New York Times.”

To Karen Auerbach of Kensington, the Times’ decision to cut those lists was more than a slight: she sees it as a serious business error. “I think the Times removing their lists has created an opportunity for the other bestseller lists to fill that vacuum,” she said. “It creates a challenging environment without those [category] lists, which were important to the community. Without [those lists at] the New York Times, it makes the USA Today and PW lists more important. Because now there is a gap that PW and USA Today are filling.”