This single math equation explains all you need to know about Facebook revenue growth, according to Citi

At its recent developers conference, Facebook laid out its grand plans for the future.

While it has ambitions in virtual reality, artificial intelligence, and internet connectivity for people all over the world, its more immediate money-maker is still advertising.

With that in mind, researches at Citi have come up with a single math equation that they believe explains everything you need to know about Facebook's revenue growth. It calls that equation The MACE Analysis.

It's not pretty, but here's the equation (click to enlarge):

So, what does "MACE" mean?

Citi broke down Facebook's ad revenue growth into its four main drivers: Monthly active user growth, change in ad load, change in ad pricing or cost per thousand ad clicks, and the change in engagement per user (meaning, how much people look at their Newsfeeds). Citi adds one to the estimated value for each of those, multiplies them together, and subtracts one.

The researchers chose not to include future revenue streams like payments, e-commerce, or transactions in its equation, and still think that Facebook can easily grow more than 20% for the next few years even without a huge increase in ads or user engagement.

In fact, plugging its own predictions into this equation, Citi thinks that Facebook will drive a three-year compound annual growth rate of 33%.

Here are the number's Citi plugged into its magical equation to get the 33%: