You’re not getting the “blazing speed” your wireless carrier promises. But it doesn’t matter.

If you believe the ads run by wireless carriers, you’d be convinced that nothing is more important than download speeds. There’s something of an arms race going one, with each combatant trotting out evidence that it delivers “blazing speed” you can’t do without. But it turns out you can – most of the time.

A study of more than 28,000 users by Nielsen indicates that about half of the files downloaded on smartphones are so small (less than .05 MB) the network doesn’t have time to reach those blazing speeds – and the users probably don’t even notice it. What about the other half? According to Nielsen, more than 80 percent of the files are smaller than 2 MB while just  3.9 percent are larger than 10 MB.

How does file size relate to speed? Nielsen explains it this way: Think of a train leaving the station. It starts out slowly, and only gradually gains momentum and speeds up. Similarly, when a user starts to download something as small as a text or as large as a video, it takes a while for the network to speed up. Small files, and remember they account for 80 percent of the traffic measured by Nielsen, have been delivered before the network is even close to its top speed.

“The larger the file size, the longer the download, and the more time the network has to pump data faster to the mobile device,” Nielsen explains. “Just because a network is capable of a fast speed doesn’t mean that’s what consumers are actually receiving.”

That’s not to say speed is never important. Streaming video files are large, and if your carrier doesn’t deliver a download speed of least 5 Mbps (the minimum recommended by Netflix for watching its videos) you’ll notice stuttering and buffering. Similarly, if you’re uploading really large photos, fast upload speeds are quite helpful.

Nielsen’s conclusions are based on the performance of 28,259 Android phones on the LTE networks of five large carriers. Although the company didn’t test iPhones, there’s no reason to assume that people download larger files if their phones are made by Apple.

Nielsen’s report is aimed at the carriers, but there’s plenty of takeaway here for consumers. Raw speed, a big selling point, isn’t the first thing to consider when you’re deciding which carrier you want to use. It’s important to note that speeds in the real world vary a good deal from city to city, from neighborhood to neighborhood and even from building to building.

When RootMetrics, a company that conducts a huge amount of wireless testing, rated the four major carriers earlier this year, it didn’t just look at speed. It considered overall quality, reliability, network speed, call quality, and data performance. You should too.

As Nielsen points out, video is becoming more and more important, and over time average file sizes will increase. But for now, speed shouldn’t be at the top of your priority list when shopping for a new carrier.