Inside Facebook

Facebook announced last week that it had crossed the 350 million worldwide active user milestone. If Facebook were a country, it would now have the third largest population in the world. Today, Facebook just crossed the 100 million active user mark in the United States — actually, more like 100.5 million, according to Facebook’s advertiser tools. That’s nearly one third of the total US population logging into Facebook each month.

Facebook has been growing in the US by at least a few million new users a month for most of the past year. The company had 98.1 million as of a week ago, having grown by around 4 million over the course of November. However, while last week may have been an especially fast-growing one for the company, the numbers it reports sometimes have a lag, or otherwise are not precise.

Anyway, if we assume the number is at least close to accurate (which it should be), this means the US is the first country to reach 100 million users, even though more than 70 percent of its 350 million worldwide monthly active users live elsewhere. The US audience is especially vital to Facebook, as the company currently makes most of its money from advertising, and the US is the single-largest advertising market in the world.

In context, the second-largest Facebook country is the United Kingdom, which has 23.2 million monthly active users. Third place is Turkey, with 16.5 million. Facebook started in the US, but has more recently grown faster in the rest of the world; today’s milestone reminds us that it is still gaining ground on its home turf — and across age groups. Here’s the age breakdown of US users, from our demographics report last week: