(CNN) -- Forget the 4G marketing hype. Which U.S. carriers really offer the fastest mobile-data networks? According to a new report from RootMetrics (a company which conducts its own field tests of wireless networks), Verizon Wireless currently offers the nation's fastest 4G -- by far. RootMetrics recently compared 4G networks from the four major U.S. carriers in 27 cities. Across all cities, Verizon performed at 4G speeds in 66% of tests. What qualifies as 4G speed? According to RootMetrics, that's a download speed of at least three megabits per second -- fast enough to download a 30-minute standard-definition TV episode in less than 10 minutes.
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Verizon performed at 4G speeds in 66% of tests -- better than AT&T, Sprint, T-Mobile
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4G speed means a download speed of at least three megabits per second
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RootMetrics compared 4G networks from the four major U.S. carriers in 27 cities
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In several markets, @placeholder's average download speeds actually exceeded the maximum speeds of the other carriers," the report said.
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According to the report, "AT&T, T-Mobile, and Sprint offered similar performances to one another overall and jockeyed back and forth behind @placeholder across the markets.
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@placeholder and T-Mobile were especially close: AT&T offered 4G speed in 40.7% of our tests, while T-Mobile recorded 4G speed in 39.5% of our tests."
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AT&T and @placeholder were especially close: AT&T offered 4G speed in 40.7% of our tests, while T-Mobile recorded 4G speed in 39.5% of our tests."
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AT&T and T-Mobile were especially close: @placeholder offered 4G speed in 40.7% of our tests, while T-Mobile recorded 4G speed in 39.5% of our tests."
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T-Mobile's performance was mostly similar to AT&T's in terms of 4G, but "disparities emerge when comparing @placeholder's non-4G tests to AT&T's.
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T-Mobile's performance was mostly similar to AT&T's in terms of 4G, but "disparities emerge when comparing T-Mobile's non-4G tests to @placeholder's.
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Sprint may offer more consumer-friendly 4G data plans than AT&T or @placeholder -- but there's a performance tradeoff.
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In addition to rating carriers' 4G performance across all of the cities, the report rated cities according to how much choice local residents have in @placeholder carriers.
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In the last year it has also published mobile performance reports for about three dozen major @placeholder metro areas.