One argument we've heard a lot is that the rise of mobile has been bad for Google's business.
According to this theory, Google's search ads aren't as effective on mobile because people don't like to shop on their phones - and when people do shop on their phones, they'd rather use an app than the Web.
But this Google-is-bad-at-mobile argument always seems so strange.
How can the rise of mobile be bad for Google when Google's mobile operating system, Android, is the world's most popular mobile operating system?
Here's how: Google doesn't actually make very much money from Android.
For starters, remember that Google gives Android away free.
Unlike Microsoft, which charges PC-makers when they put Windows on a laptop or desktop computer, Google doesn't actually make smartphone makers pay to install Android on the phones they sell.
The idea has always been that giving Android away free will put the Web into more people's hands, and that will lead to more mobile Web searches and clicks on Google's search ads.
But according to a new report from a group of Goldman Sachs analysts, Android users aren't clicking on very many Google ads.
Earlier this week, Goldman's analysts estimated that Google did $11.8 billion in mobile search revenue in 2014.
Goldman estimated that 75% of that revenue, $8.9 billion, came from Web searches made using iPhones and iPads.
That means that, at most, Google generated $3 billion from searches made on Android devices in 2014.
$3 billion is a paltry amount compared to Google's overall business, which generated $66 billion in the last twelve months. For further context, consider that Facebook generated more than $2.65 billion in mobile ad revenues during the fourth quarter of 2014 alone.
It makes you wonder: Will Android ever become a big business?
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On the one hand, it may not matter. Android has effectively destroyed Microsoft's Windows hegemony. And it prevented Apple from running away with the phone market the way it ran away from the MP3 player market like it did with the iPod.
On the other hand, it has ~1 billion users. Typically when a product hits a billion users, it figures out a good monetization plan. It's unclear Google has any plan to make big money from Android. That would be fine if, as 5 years ago, everything was going great for Google. But, today, things are a bit more tricky.
We're taking a closer look at Google, which seems to be stuck in something of a rut. We'd like to hear from Googlers and ex-Googlers. Email nicholas@businessinsider.com or jdonfro@businessinsider.com