Good news: your cell phone network's performance is faster than it was a year ago. But the rate at which network speeds are increasing has slowed down, and all those unlimited data plans may be too blame.
That's the finding from network testing firm Ookla, which just published the results of its Speedtest network testing for the first half of 2017. According to the user-generated testing, T-Mobile has the fastest network of the four major carriers, beating out second-place Verizon. AT&T was a solid third place, while Sprint finished fourth.
All four carriers boosted their speeds compared to a year ago, Ookla said, as overall network speed rose 19 percent over the same period in 2016. However, that was slower year-over-year growth than the 33 percent increase in speed Ookla recorded during the first half of 2016.
One of the culprits could be increased traffic on wireless networks as more of us take advantage of wireless data plans to stream videos, send messages and browse on the go. Indeed, Ookla noted a dip in speed between the first and second quarters of 2017. That's not coincidental timing: both Verizon and AT&T launched unlimited data plans around that time, matching the offerings of T-Mobile and Sprint.
More users with unlimited data could lead to some slowdowns in average speed, particularly as carriers throttle the speeds of customers who use a lot of data in a month. Both AT&T and Verizon start slowing speeds if you go over 22GB of data in a billing period. (Sprint and T-Mobile throttle, too, though their thresholds are a little bigger at 23GB and 32GB, respectively.)
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The way some carriers handle their unlimited plans could also contribute to the slowdown in speed increases. AT&T's less expensive unlimited plan caps data speeds at 3 Mbps, for example. Last month, Verizon reshuffled its unlimited plans with the cheaper option allowing the carrier to slow down speeds if its network is congested.
"It seems likely we’re seeing reduced performance due to high usage de-prioritization and consumer plan choice," Ookla said in its report.
Specifically, Ookla noticed an increase in test results with download speeds under 5 Mbps for Verizon and AT&T. Sprint and T-Mobile saw fewer results below 5 Mbps for the first half of 2017, compared to the end of last year.
Ookla is the second testing firm in recent months to see unlimited plans having an impact on some wireless networks. In August, OpenSignal's report on network performance during the first half of 2017 claimed that network speeds were slowing at AT&T and Verizon.
Lynette Luna, a principal analyst at GlobalData Technology, notes that data congestion has been on the rise since Apple's first iPhone popularized smartphones 10 years ago. "The most obvious ways we've seen carriers mitigate data congestion is through data caps and service tiering where consumers pay less for lower-quality video," Luna said. AT&T's cheapest unlimited plan caps video streaming at 480p resolution and Verizon's new Go Unlimited plan does the same; the basic T-Mobile One plan has that same restriction.
Expect that trend to continue, Luna said, as "customers who want higher-quality video quality will be asked to pay for it."
"Verizon's move [to new unlimited plans] also potentially sets the stage for carriers to start implementing plan tiers that charge for higher data speeds or discount for lower ones," Luna added. "In fact, Cricket Wireless' two lines for $80 unlimited-everything plan (Cricket Unlimited 2) offers an example in that the plan limits data speeds to 3 Mbps (not the usual 8 Mbps)."
For its part, Verizon noted that Ookla's report confirms that its network offers widespread coverage and that it had the fastest speeds in many of the cities Ookla looked at.
"Our network has never been stronger," said Mike Haberman, Verizon vice president of wireless network operations, in a statement to Tom's Guide. "Our network philosophy is simple: provide the largest coverage, the most reliable service and the most consistently fast speeds. This makes up the customer experience."
Verizon also thinks the crowd-sourced data Ookla uses has its limits. "Crowd sourced data does not provide a like-for-like comparison. Depending on how you slice the data it can say different things," said spokesperson Howard Waterman, contending that Verizon's analysis of Ookla data for the top 125 gives the carrier a 40 percent margin in median speeds over T-Mobile.
Not surprisingly, T-Mobile had a different take on the report, pointing out that this was the 14th straight quarter where it topped Ookla's test results. “Millions of wireless customers across the US have spoken — again — and they’ve shown that T-Mobile is the master of all things unlimited, while Verizon is the master of none,” T-Mobile chief technology officer Neville Ray said in a statement.
As for AT&T, Ookla said the carrier had maintained performance amid increased competition, though it saw a notable drop in performance after AT&T rolled out unlimited data plans. Ookla did note an improvement in performance in recent months, though.
While Sprint brought up the rear in Ookla's Speed Score rankings, the testing firm did find the carrier had made significant improvements over last year, with its mean download speed improving. Ookla also thinks Sprint is poised for more gains going forward.
Editors' Note: Updated with additional comment from Verizon.
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Philip Michaels is a Managing Editor at Tom's Guide. He's been covering personal technology since 1999 and was in the building when Steve Jobs showed off the iPhone for the first time. He's been evaluating smartphones since that first iPhone debuted in 2007, and he's been following phone carriers and smartphone plans since 2015. He has strong opinions about Apple, the Oakland Athletics, old movies and proper butchery techniques. Follow him at @PhilipMichaels.