Apple is working with more than 100 news publishers to put content in the News app for iOS, but there’s a slight hiccup: Neither Apple nor the publishers know how many people are reading News.

According to the Wall Street Journal, Apple has been underestimating the number of News readers it reports to publishers, though the company didn’t say how or why the problem happened, or when it might be fixed.

The Wall Street Journal, the New York Times, Washington Post, and other major news publications can’t be happy about the glitch, which means they’ve been giving their advertisers wrong information. Publishers can sell their own ads in the app and reap 100 percent of the revenues, or they can let Apple sell ads on their behalf and keep 70 percent. But when publishers don’t have an accurate view of how big their audience is, that leads to lower ad rates and is generally bad for business.

Eddy Cue, Apple’s senior VP of software and services, told the WSJ that 40 million people have used Apple News, but that number appears to include everyone who’s ever opened the app. It’s unclear how many people regularly read News, but publishers told the WSJ they weren’t that impressed with the numbers Apple was giving them.

Why this matters: The News app is easy to set up and use, but people already have so many other options, from read-it-later services like Pocket to Facebook’s Instant Articles and Snapchat Discover. Publishers are all in with Apple, because News is a built-in app that comes preinstalled on iPhones and has a wide reach, but if they feel Apple can’t provide accurate stats on the app’s usage, the content they’re putting in News might dry up and fade away.

Are you regularly using Apple News? Why or why not? Let us know in the comments.