Facebook stunned yesterday with its report that mobile advertising represented 41 percent of its total ad revenue in the second quarter of 2013. In the first quarter of 2013, it totaled a then-hailed 30 percent, bumping that key ratio by more than a third in just a fourth of a year. On a dollar basis, Facebook’s mobile advertising grew more than four times as much as its desktop-sourced advertising incomes in the most recent quarter.

However, looking backwards, last quarter’s mobile ad growth is less astounding when placed into context. From the third to fourth quarter of 2012, Facebook juiced its ad revenue as a percentage of total ad income by 9 percent. From the last quarter of 2012 to the first quarter of 2013, growth was 7 percent. Taking into account the 11 percent gain reported yesterday, Facebook has averaged 9 percent growth in its mobile ad revenue as a component of its larger ad top line for the past few quarters.

This allows us the ability to make basic predictions. Facebook yesterday noted on its earnings call that mobile advertising revenues will eventually outstrip desktop ad income. But when? Well, we can predict. If mobile advertising revenues continue at their average rate of the past few quarters, Facebook should earn precisely as much from desktop and mobile advertising platforms in the current quarter.

The math is simple: Facebook ended the most recent quarter with a 41/59 split between mobile and desktop ad income. If mobile revenues are growing by 9 percent quarterly — again, on average — 41 and 9 make 50, leaving the remaining 50 percent for desktop ad revenues.

Adding another 9 percent to Facebook’s mobile ad revenue as a percentage of its total ad income, and we could wrap the year where the second quarter finished, but in reverse, with mobile revenues comprising 59 percent of total ad income, and desktop just 41 percent.

This feels, prima facie, optimistic. Are we being too generous?

There is always a risk in any form of prediction, as future market dynamics are outside of our vision, and will always remain so. That said, we can take mild refuge in the fact that our average rate of mobile ad growth, again as a percentage of Facebook’s total advertising top line, is *under* the most recent quarter’s rise; this means that we are anticipating Facebook to under-perform its most recent quarter moving forward.

This gives us some breathing room in our predictions. Here’s the chart:

If mobile revenue is so strong, where does that leave desktop advertising incomes? Well, as it turns out, Facebook’s desktop advertising business is all but not growing. We can deduce this by subtracting the percentage of Facebook’s mobile ad revenue from its total advertising income, leaving us with its desktop-sourced figure. Let’s have some fun:

- Facebook’s total advertising revenue was $1.25 billion in the first quarter of 2013. Of that, 30 percent came from mobile. That means 70 percent came from desktop sources. Seventy percent of $1.25 billion is $875 million.
- Facebook’s total advertising revenue was $1.60 billion in the second quarter of 2013. Of that, 41 percent came from mobile. That means 59 percent came from desktop sources. Fifty-nine of $1.60 billion is $944 million.
- $944 million – $875 million = $69 million. That, assuming that Facebook has its numbers in place, is the delta between Q1 and Q2 for Facebook’s desktop advertising business.

That’s not much. Not only is Facebook sourcing a growing percentage of its revenue from mobile platforms, but its revenue growth is increasingly coming from a smartphone near you.

Let’s get to the bottom of the final number: In dollar figures, how much did Facebook’s mobile ad revenue grow from the first to second quarter? I’m glad you asked. Let’s find out:

- Facebook’s total advertising revenue was $1.25 billion in the first quarter of 2013. Of that, 30 percent came from mobile. Thirty percent of $1.25 billion is $375 million.
- Facebook’s total advertising revenue was $1.60 billion in the second quarter of 2013. Of that, 41 percent came from mobile. Forty-one percent of $1.60 billion is $656 million.
- $656 million – $375 million = $282 million.

So, Facebook’s mobile revenue grew by a quarter billion dollars in the second quarter. Not bad, given that as a percentage gain it works out to around 75 percent. And, perhaps more importantly, the $282 million figure is more than four times our previous $69 million sum. Therefore, mobile ad revenues on a dollar basis grew four times as fast as desktop advertising incomes in the most recent quarter.

Mobile-first, indeed.

*Top Image Credit: Randy Lemoine*