Unless applying for a loan or during an interview, salary is usually a sensitive topic. Many people tend to dislike talking about how much they earn.

Facebook users should know that nothing is private on the platform. Anything that is shown on their News Feed, is based on their interests, their friends' interests, interactions on photos, videos, news and many many more.

But using a patent it calls "online service," Facebook can personalize users' News Feed using another criteria: users' socio-economic status.

And it does that without having to know their incomes.

Here, the company is exploring more ways to know more about its users.

And for this to work, Facebook relies on the information that users may have uploaded voluntarily, such as through photos, check-ins, status updates, and more.

Using the data, Facebook’s algorithm can work to determine its users' Class, such as working class, middle class, or upper class. For example, users who own up to six devices "belong to the upper class".

The Patent Publication illustration above, shows the algorithms' decision tree that guesses whether a user is a middle person or not. This categorizes the user by the number of devices he’s using/logged in, his highest education qualification, where he lives, and so forth.

"The classifiers use models that are trained using features based on global information about a population of users such as demographic information, device ownership, internet usage, household data, and socio-economic status," states Facebook's patent application.

This system would allow Facebook to more accurately target users with content and advertising tailored to their social class, the company said. And here, Facebook can use a multitude of sources for the classifiers.

For privacy concerned individuals, this is scary.