-By Mike Beirne, Brandweek

CHICAGO Facebook took a step toward standardizing the wild world of Web metrics by switching its engagement rating for applications from reporting daily usage to measuring monthly active users.

The social networking site disclosed the change last week via a company blog aimed at an audience of developers. The goal is to help developers focus on "longer-term engagement" and show them "the number of users who visit [their] application over a longer time frame than just one day," according to Facebook.

"The new metric will force widget developers to work differently," said Sonya Chawla, managing director of advertising at Slide, a San Francisco firm that has developed top applications for Facebook like SuperPoke and TopFriends. "A daily count measures a flashy application that does one thing like show a movie preview, for example. A longer time frame [metric] will force widget developers to seek longer term engagement with their widget applications."

Internet marketing research firms like comScore and Nielsen already report engagements -- the number of times a mini software application with video, games and other content is used by a social network member -- on a monthly basis. Software developers and marketers that use widgets in their digital campaigns check monthly reports to see if their applications are among the most popular and have momentum.

Facebook, Palo Alto, Calif., opened its social network to third party developers last May. Since then, more than 24,000 applications have been built for Facebook. Initially, installments -- the number of times an application is installed on a Facebook member's profile page -- was a measure used to rank application. However, that metric has fallen out of favor with digital agencies and marketers because vendors who are paid by clients on a per-install basis can manipulate it.

"The more data perspectives the better," said Peter Blackshaw, evp, Nielsen Online Digital Strategic Services. "There's certainly something to be said for offering developers a longer term engagement metric. This looks to be a net positive, especially if it's truly grounded in user or application developer feedback. I think we're in the early stages of converging around the right engagement metric."

The Nielsen Co. is the parent company of Adweek and Brandweek.