If your Netflix or YouTube stream is crappy, there’s a good chance your wireless provider is just trying to milk you for more money, according to new research out of Northeastern University.

While ISPs have historically claimed that they only slow down network traffic in very specific cases of network congestion to prevent network slowdowns for other users, the University's latest research indicates that’s not true. Working with other researchers, Dave Choffnes, assistant professor of computer and information science at Northeastern, developed an app named Wehe. Wehe was then used to conduct half a million data traffic tests across 161 countries to help determine which ISPs routinely hamstring streaming performance of services like YouTube and Netflix. His findings: nearly every major wireless provider in the States specifically throttles video (aka “differentiation”), even when the network is perfectly capable of handling the load. “There’s no evidence that any of these policies are only happening during network overload,” said Choffnes is a statement. “They’re throttling video traffic even when the network doesn’t need to. It happens 24/7, and in every region where we have tests.” Different wireless carriers were more aggressive with this throttling than others, Choffnes notes. A full breakdown of the instances of throttling found that Verizon was by far the worst culprit, with 11,100 instances where a video service was slowed on a test device occurring between January and May of this year. AT&T was second worst with 8,398 instances of slowdowns.

So if carriers aren’t throttling video to help manage network congestion, what are they doing? They’re intentionally slowing video in a bid to make even more money off of consumers that already pay some of the highest prices for mobile data in the developed world, recent cellular plan changes suggest. The kind of video differentiation Choffnes and his team is observing has increasingly occurred as wireless carriers sell tiers of “unlimited” data plans where users are forced to pay more money if they want to view video streams the way they are intended.

For example, Verizon now sells three different grades of unlimited data plans, the lowest of which automatically throttles all video to 480p unless users pony up additional money for a less-restrictive option. Only if you pay substantially more money are you able to view videos in full HD, and 4K-quality video is banned on the company’s network entirely. Whether creating such arbitrary restrictions to make more money is a net neutrality violation has long been a point of contention. The FCC’s recently-discarded 2015 net neutrality rules prohibited arbitrary throttling except in cases of “reasonable network management,” though the definition of “reasonable” has pretty consistently been abused by mobile carriers.

Critics have long charged that such differentiation opens the doors to worse offenses down the road, as ISPs attempt to impose all manner of restrictions you’ll then have to pay extra to avoid. Sprint, for example, has flirted with charging users more money if they want to avoid the arbitrary throttling of video games and music.

Whether or not this technically constitutes a net neutrality violation, cellular providers’ vague definition of “unlimited data” continues to confuse consumers and cause problems, as the recent throttling of California firefighters made clear.

And that’s where the FCC’s net neutrality rules proved helpful. As part of the rules, ISPs were required to be utterly transparent about their network management practices. With those rules now discarded after ample telecom sector lobbying, the only remaining transparency rules left are completely voluntary and can be ignored by ISPs without meaningful penalty.

In this new reality, crowdsourced data and researchers like Choffnes are going to be the last line of defense between consumers and the arbitrary, anti-competitive behavior of their mobile carriers.

Even then, Choffnes told me over e-mail that his test still has its limitations in terms of identifying more technical potential net neutrality violations.

“Many kinds of net neutrality violations that Wehe doesn't look for (e.g., paid prioritization, paid peering) are difficult, if not impossible, to measure without cooperation from the ISP,” Choffnes told me.

Still, maintaining a public database of how ISPs treat individual apps goes a long way in bringing some additional transparency to the end user. And if consumers want the government to actually hold carriers accountable for (and prohibit) shady business practices, they should continue to advocate for meaningful net neutrality laws (preferably not written by ISPs, that is).