If you think mobile data service is mediocre in Denver, a new report agrees. Metro Denver ranked among the five worst U.S. cities for overall mobile performance, according to researcher RootMetrics.

At a lowly No. 121 out of 125 cities, Denver’s overall score was worse than Colorado Springs (No. 113) and the much smaller cities of Rockford, Ill. (No. 5) , Port St. Lucie, Fla. (No. 6) and Shreveport, La., (No. 29).

“Specifically in Denver, the low ranking can be attributed in part to lower-than-average performance in network speed and data performance,” RootMetrics’ Annette Hamilton said.

But it’s also relative: Denver’s major mobile carriers offered better service elsewhere, she said, adding that “the larger carriers did less well relative to their other markets.”

The RootMetrics report, which covers the second half of 2015 and is to be released Tuesday, had a three-way tie for the best cities for mobile performance: Atlanta, Chicago and Indianapolis. All scored 98.2 points. Denver’s scored 93.8.

The higher the score, the fewer dropped calls, faster download speeds and better regional coverage.

Denver’s score was hurt by slow data and network speeds, which consumers use more these days to view video and other content on smartphones.

AT&T and T-Mobile dragged down Denver’s overall rank when the two posted median download speeds of 6.7 and 6.8 megabits per second, respectively.

Sprint offered the fastest speed in Denver, at 12.8 mbps, while Verizon came in at 8.8 mbps.

But those are snail-paced compared to the median download speeds experienced by Atlanta consumers. Verizon ranked the highest at 35.9 mbps, with Sprint the slowest, relatively, at 19.2 mbps.

Denver’s network reliability, which ranked in the bottom fifth, was also a factor. “Reliability is the most important mobile performance metric because if you can’t get connected and stay connected, it doesn’t matter how fast the network goes,” she said.

In the last couple of years, RootMetrics has seen major improvement in performance by Denver’s mobile carriers. All have scored above 90 points since the middle of 2014.

Denver’s mobile carriers have been investing in their networks. Last August, T-Mobile added 700 MHz technology in Colorado to improve calls made indoors and in rural areas. But in order to see the benefit, consumers — and RootMetrics — must buy 700 MHz phones.

Denver, whose population is the 18th-largest nationwide, wasn’t the only larger city with a dismal rank. New York City, the most populated, came in at No. 76, while second-most-populous Los Angeles ranked No. 94.

Typically, Hamilton added, when a city scores low, it’s due to network congestion or interference. In other words: a growing population. Denver is among the nation’s fastest growing cities.

“In general, as carriers add customers, we have seen that networks slow down until the network catches up again. We can’t say for certain that this is or will be happening in Denver, but it is something we have seen in the past,” she said.

At least, she added, carriers seem to be paying attention to the area.

“We can note that when it comes to LTE service, the Denver area is fairly saturated, showing that carriers are making efforts to improve their overall network performance in the area,” she said.

Tamara Chuang: tchuang@denverpost.com or visit dpo.st/tamara

Best and Worst Mobile Performance

In testing mobile service in 125 cities, researcher RootMetrics ranked Denver among the worst. RootMetrics sent testers to Denver last August and conducted 20,000 tests to check data speeds, dropped calls, coverage and reliability.

TOP FIVE:

1. Atlanta

1. Chicago

1. Indianapolis

4. Sacramento, Calif.

5. Rockford, Ill.

BOTTOM FIVE:

121. Denver

122. Santa Rosa, Calif.

123. Lancaster, Pa.

124. Omaha

125. Hudson Valley, N.Y.

Source: RootMetrics

Updated March 8, 2016 at 10:37 a.m. This story has been updated to correct information provided by a source and now accurately reflects RootMetrics spokeswoman Annete Hamilton’s opinion on the importance of network reliability.