faceb.pngFacebook has delivered on a promise to show how many users are actively using its popular platform.

Responding to urgent demand for such stats by eager developers and others, the company now shows how many “daily active users” each Facebook application has. This user “engagement” calculation is based on Facebook’s analysis of pageviews, click-throughs between pages, and actions taken within a page — including playing a Flash-based game or video.

It follows Facebook’s promise Monday to deliver such tools — an effort to provide public measurements about usage of applications developed by third parties, among other changes.

The effect is similar to a web site being forced to publicly reveal its daily traffic numbers, a bit like walking around naked for anxious developers. Of course, having this information public is great for advertisers because they have a clearer view of which applications have Facebook user’s attention — where they can get the most bang for their buck on the site.

Many companies with Facebook applications have already been featuring such attention-focused metrics. Facebook is considered more effective than other social networks at capturing its users’ attention through news feeds, pokes and other carefully designed features, as Jeremy Liew wrote yesterday. Myspace widgets have lower click-through rates than Facebook apps. Users stay on those widgets for less time than on apps, Liew finds.

Strikingly, though, nearly all of the applications with millions of users appear to average daily active user rates between approximately ten and twenty percent, as can be seen here — while many applications with smaller total users boast far higher daily active user rates.

Third party developers are also developing third-party measuring tools.

Adonomics, formerly Appaholic, has been tracking growth and changes occurring among Facebook applications. The company says it will also provide “stock-market style analyses” of Facebook features, hoping to provide even more information about how much applications are worth in terms of advertising dollars.