Charles Arthur explains on The Guardian why an 80% market share might only represent half of smartphone users.

TheNextWeb lamented Nike’s choice not to bring their FuelBand app to Android.

For many, this glaring omission in Nike’s technological armory is astounding given that, well, Android represents somewhere in the region of 80% of the smartphone market.

MarketWatch reported that Android achieved a market share of 80.6%.

It’s simply wrong, though, to extrapolate from that to think that four in five smartphones in peoples’ hands are Android-powered. Here’s the reality: at the time this was written, more than 40% of the smartphones in use in the US (a key market for Nike) were iPhones. Only about 51% of the smartphones in peoples’ hands in the US are Android phones. The ratios are more in Android’s favour elsewhere, but nowhere outside of China (and perhaps India) would you find four in five smartphone owners using an Android phone.

Data from Google’s Android developer dashboard paints a different picture.

The newest software, “Jelly Bean” (which actually covers three different numbering versions), accounts for 52.1% of the devices. Yet Jelly Bean is the software powering all those new Android phones – the ones that were the 80% in the past quarter. Clearly, the installed base doesn’t reflect the market share number.

If market share of tablets drops from 50% to 30%, does it mean that less tablets were sold?

No, that’s not what that data tells you. What if the total number of tablets being sold has doubled? If last year there were 100m tablets sold in total, and this year 200m, then last year the figures would be 50m tablets and this year 60m. (Those aren’t the numbers. They’re just for illustration.)

So if you don’t have the absolute numbers, you don’t know what’s happening.