I was using Google search on my cellphone a few days ago and I thought my connect time was sluggish. That prompted me to take a look at the download speeds on cellular networks, something I haven’t checked in a while.

There are two different companies that track and report on mobile data speeds, and the two companies report significantly different results. First is Ookla, which offers a speed test for all kinds of web connections. Their latest US speed test results represent cellphone users who took their speed test in the first half of this year. Ookla reports that US cellular download speeds have increased 19% over the last year and are now at an average of 22.69 Mbps. They report that the average upload speeds are 8.51 Mbps, an improvement of 4% over the last year. Ookla also found that rural mobile broadband speeds are 20.9% slower at urban speeds and are at an average of 17.93 Mbps.

The other company tracking mobile broadband speeds reports a different result. Akamai reports that the average cellular download speed for the whole US was 10.7 Mbps for the first quarter of 2017, less than half of the result shown by Ookla.

This is the kind of difference that can have you scratching your head. But the difference is significant since cellular companies widely brag about the higher Ookla numbers, and these are the numbers that end up being shown to regulators and policy makers.

So what are the differences between the two numbers? The Ookla numbers are the results of cellphone users who voluntarily take their speed test. The latest published numbers represent tests from 3 million cellular devices (smartphones and tablets) worldwide. The Akamai results are calculated in a totally different way. Akamai has monitoring equipment at a big percentage of the world’s internet POPs and they measure the actual achieved speeds of all web traffic that comes through these POPs. They measure the broadband being used on all of the actual connections they can see (which in the US is most of them).

So why would these results be so different and what are the actual mobile broadband speeds in the US? The Ookla results are from speed tests, which last less than a minute. So Ookla speed test measures the potential speed that a user could theoretically achieve on the web. It’s a test of the full bandwidth capability of the connection. But this is not necessarily the actual results for cellphone users for a few reasons:

• Cellphone providers and many other ISPs often provide a burst of speeds for the first minute or two of a broadband connection. Since the vast majority of web events are short-term events this provides users with greater speeds than would be achieved if they measured the speed over a longer time interval. Even with a speed test you often can notice the speed tailing off by the end of the test – this is the ‘burst’ slowing down.
• Many web experts have suspected that the big ISPs provide priority routing for somebody taking a speed test. This would not be hard to do since there are only a few commonly used speed test sites. If priority routing is real, then speed test results are cooked to be higher than would be achieved when connecting to other web sites.

The Akamai numbers also can’t be used without some interpretation. They are measuring achieved speeds, which means the actual connection speeds for mobile web connections. If somebody is watching a video on their cellphone, then Akamai would be measuring the speed of that connection, which is not the same as measuring the full potential speed for that same cellphone.

The two companies are measuring something totally different and the results are not comparable. But the good news is that both companies have been tracking the same things for years and so they both can see the changes in broadband speeds. They also both measure speeds around the world and are able to compare US speeds with others. But even that makes for an interesting comparison. Ookla says that US mobile speed test results are 44^th in a world ranking. That implies that the mobile networks in other countries make faster connections. Akamai didn’t rank the countries, but the US is pretty far down the list. A lot of countries in Europe and Asia have faster actual connection speeds than the US, and even a few countries in Africa like Kenya and Egypt are faster than here. My conclusion from all of this is that ‘actual’ speeds are somewhere between the two numbers. But I doubt we’ll ever know. The Akamai numbers, though, represent what all cell users in aggregate are actually using, and perhaps that’s the best number.

But back to my own cellphone, which is what prompted me to investigate this. Using the Ookla speed test I showed a 13 Mbps download and 5 Mbps upload speed. There was also a troublesome 147 ms of latency, which is probably what is accounting for my slow web experience. But I also learned how subjective these speeds are. I walked around the neighborhood and got different results as I changed distances from cell towers. This was a reminder that cellular data speeds are locally specific and that the distance you are from a cell site is perhaps the most important factor in determining your speed. And that means that it’s impossible to have a meaningful talk about mobile data speeds since they vary widely within the serving area of every cell site in the world.