Since the demise of net neutrality, US telecoms have increased the amount of throttling they impose on customers trying to watch mobile video through services like Netflix and YouTube, according to new research from a group of researchers at Northeastern University and the University of Massachusetts, Amherst. The study, the findings of which were published first by Bloomberg today, reveals the extent to which companies like AT&T and Verizon have taken advantage of lax government regulation under President Donald Trump to limit data speeds for customers.

This isn’t presenting entirely new information. All four big carriers in the US now offer unlimited data plans that restrict streaming video on mobile devices to 480p by default, in an apparent effort to manage network traffic, reduce congestion, and ensure that these companies don’t need to upgrade network infrastructure unless absolutely necessary.

The study, however, reveals how often this is happening and to which apps. It also provides data on the uptick in this behavior since Obama-era net neutrality regulations were repealed by Federal Communications Chairman Ajit Pai, who led the vote to do so in December 2017 before the order went into effect in June of this year. The research is not yet publicly available; it will be submitted for peer review as it amasses a full year’s worth of data.

Researchers gathered data from the Wehe app, which monitored carrier throttling

The research was conducted by getting around 100,000 people to sign up for a mobile app called Wehe, which monitored network traffic for participating users to determine when an app experienced “differentiation,” as the study puts it. The app conducted around 500,000 tests, monitoring over 2,000 service providers in 161 countries.

AT&T and Verizon were by far the most egregious throttlers, differentiating delivery speeds for streaming video 8,398 and 11,100 times, respectively. T-Mobile and Sprint differentiated traffic 3,900 times and 339 times, respectively. Most of this differentiation equates to throttling, the study concludes, meaning US carriers are slowing the delivery speed of the data based on the type of data it is — a violation of one of the pillars of modern net neutrality principles. “If you are a video provider, you have a patchwork of different carriers doing different things to your network traffic,” said David Choffnes, a co-author of the study and the developer of the Wehe app, in an interview with Bloomberg. “And the patchwork can change any time.”

AT&T and Verizon do not hide that their networks are actively throttling distinct traffic types, although the carriers prefer phrases like “network management,” terms like prioritization, and other euphemisms that disguise the fact that data speeds are artificially slowed down. Right now, most unlimited data plans from the big US carriers will throttle all traffic once you exceed a certain number of gigabytes used, typically around 22GB or 25GB.

AT&T, Verizon, and T-Mobile also restrict video to 480p unless you pay for certain types of plans that allow you to stream in HD, by turning off a certain setting either on your phone or doing so only through the carrier’s website. Oftentimes, this throttling is presented as a feature, like AT&T’s Stream Saver, that’s designed to save customers from careless data use that might eat up too much of their monthly allowance.

Since the FCC became a Republican-controlled body under Trump, US carriers have significantly altered their offerings and, in many cases, made their plans worse by restricting how much “unlimited” data customers are actually afforded and what they can do with it. As the study makes clear, this is a direct result of FCC leniency and has occurred in lockstep with Pai’s initial announcement to repeal net neutrality protections last year and his eventual following through in December.

US carriers have made their ‘unlimited’ plans more confusing and restrictive

Last summer, after all four major US carriers started offering unlimited plans with huge caveats in February 2017, Verizon removed the ability to stream HD videos on mobile phones entirely from all of its plans with its introduction of three new plans with reduced streaming video privileges and a number of throttling thresholds and hotspot restrictions. Earlier this year, Sprint made its current unlimited plan worse and added a more expensive version of it in a bid to get customers to pay more money per month.

AT&T also more than doubled the administration fee it charges every wireless customer to $1.99, citing “cell site maintenance and interconnection between carriers.” Meanwhile, a July report from the US Labor Department indicates that cellphone plans are getting more expensive after two years of price cuts now that telecoms have hooked customers into increasingly nebulous unlimited plans and feel the need to offset the cost of large mergers and acquisitions.

All that being said, Choffnes and his fellow researchers hope the debate around throttling and not-so-unlimited data plans is reaching a tipping point. Recent news stories seem to suggest a heightened controversy around telecom behavior is brewing. Late last month, Verizon was caught throttling the data connections of emergency firefighters battling raging wildfires in Northern California’s Mendocino County.

Meanwhile, California passed the nation’s strongest net neutrality protections at the state level last Friday, with the bill now headed to Governor Jerry Brown’s desk for signing. The move could significantly shift how the government regulates mobile internet providers now that the FCC has punted the responsibility to the less powerful FTC, and it sets up a model for other states to follow suit and apply pressure to regulatory bodies.