Available Data Shows Facebook User Numbers Growing Quickly, or Slowly, or Falling

Did Facebook have fewer monthly active users in the United States at the start of June than it did at the start of May? What about user counts in other early-adopter countries like Canada and the United Kingdom? Is the company continuing to gain as many new users around the world now as it has in recent years?

As we covered yesterday, Facebook appears to have had fewer monthly active users at the start of June than at the start of May in the US and a few other countries — at least according to one data source — even as it has grown bigger than ever worldwide. Although today a person close to the company tells us that the site is “still growing in the US.”

Our data source was Inside Facebook Gold, our tracking service that shows country-by-country monthly active user counts, based exactly on the data that Facebook provides in its advertising tool. It showed Facebook falling from 155.2 million at the beginning of May to 149.4 million at the beginning of June, but growing by 11.8 million monthly actives around the world to reach 687.1 million over the same period.

Because this data can be buggy, delayed, or otherwise unclear, we regularly compare it against what leading third party measurement services show. Here’s the latest data available from Compete, comScore, Google Ad Planner and Quantcast.

A word of warning, though: Each of these other services has its own methodologies, and its own delays and bugs, so it’s important to look for trends that emerge from multiple sources over the months, not just what a given source says on a given month. Facebook, for example, self-reports its data in monthly active users, which isn’t exactly the same measure as the “monthly unique visitor” metric that third parties provide.

As you can see from our past posts, as well as from the data below, each data source does not exactly match with the others (here are the three most recent editions, if you’re interested). Let’s get started.

Compete

May stats are not yet available, but looking back to April, the firm shows Facebook falling from 140.7 million monthly unique visitors in March to 137.9 million in the US. In contrast to multiple other sources, Compete has shown Facebook gaining and losing users month-to-month over much of the past year.

It also shows Facebook’s most direct social product rivals, Twitter and MySpace, also losing users in April.

ComScore

While often more in line with the data in Facebook’s ad tool, comScore’s data tends to diverge a bit in the US and a lot internationally — or at least that’s what we’ve observed in the past (take a look at the top graph in this story for another divergent month: January of 2011).

In May, Facebook grew by 3.16 million monthly unique visitors, according to the firm, to reach 157.2 million in the country. It’s not clear why comScore is showing growth while Facebook itself is showing a loss. Twitter, meanwhile, made back some losses from April, while Myspace lost some of its gains from that month.

ComScore doesn’t have May worldwide numbers available yet, so here’s a look at March and April. Facebook had a slow month, growing by around 5 million worldwide, while MySpace made some unexpected gains, and Twitter fell again after many months of growth.

Google Ad Planner

In striking contrast to all other available stats, Google’s DoubleClick Ad Planner tool shows Facebook with 890 million unique visitors. It’s not clear why. The graph you see below shows Google’s count of Facebook’s daily unique visitors, based on browser cookies. This usage measure appears to have declined slightly from a high at the start of April back to 300 million.