Verizon, AT&T, and Sprint all lag behind T-Mobile when it comes to 4G LTE speeds. That is according to the newest Ookla Speedtest report, which analyzed crowdsourced test results taken during the first and second fiscal quarter of 2017.

T-Mobile is the fastest carrier in 40 of the U.S.’s 100 most populous cities, according to Ookla. Subscribers speeds regularly exceeded Ookla’s Acceptable Speed Ratio — a download rate of at least 5 Mbps —  78.1 percent of the time, ahead of Verizon Wireless (77.8 percent), AT&T (75.9 percent), and Sprint (64.9 percent). T-Mobile scored the highest in Ookla’s Speed Score rankings, an average of low-end, median, and top-end speeds.

It’s the 14th quarter in a row in which T-Mobile came in first.

Ookla attributes T-Mobile’s achievements to its infrastructural investment, which saw the rollout of the 700MHz spectrum and 4G LTE in new markets. And it pegged competitors’ declining speeds on unlimited data plans. In the fourth quarter of 2016 before the launch of the unlimited plans, Verizon and AT&T’s lowest-end download speeds (those under 5 Mbps) shot up compared to the period before unlimited data plans were widely available, according to Ookla. T-Mobile and Sprint saw the opposite effect.

“[Not] all carriers are responding equally to the performance demands of unlimited data plans,” Ookla said.

T-Mobile did not lead every category. Its coverage fell short of AT&T and Verizon’s, which made up 27.3 and 51.6 percent of Ookla’s test samples in rural areas.

Ookla spotlighted Verizon in particular, highlighting the network’s “network densification” and deployment of small cells in urban, suburban, and commercial areas. “Verizon’s rural coverage is laudable,” Ookla said. “Verizon has been able to maintain solid performance in areas of high traffic [despite] a drop in performance […] since Verizon launched Unlimited.”

And in terms of U.S. as a whole, carriers have a long way to go.

Despite a 19 percent improvement in average mobile download speeds in the U.S., the country fell to 44th in the world for download speed, behind Fiji and Germany, and customers in rural areas saw an average download speeds 20.9 percent slower than the nation as a whole. Average mobile upload speeds improved just four percent to 8.51 Mbps, Ookla said, putting the U.S. 65th in the world for upload speed (behind Mongolia).

“Mobile performance in the U.S. is improving, but not uniformly,” Ookla said. “Mobile data consumption is expected to continue to grow over the next year, and carriers will need to find creative ways to increase the […] efficiency of their networks.”

Ookla said it looked at data from 100 most populated Cell Market Areas (CMAs), a geographic determination used by the Federal Communications Commission (FCC) to identify broadband markets in the U.S., to compile its report, including 3 million unique mobile devices.