If there's one thing I've learned in life, it's that size matters. Whether we're talking about popcorn at the movies, engagement rings or grade point average, there is no getting around it. Naturally, the same is true with Facebook Page communities, right?

Or is it really about the quality of the popcorn or the clarity of the ring (let's agree to leave GPA out of this)? Knowing what we should measure is the first step in understanding what these metrics actually tell us.

An article recently published by eMarketer shared the results of a Visibli study showing how fan engagement rates decline as a Facebook Pages add more fans. Essentially, the article is saying that the bigger the page, the lower the engagement. The fact that anyone is having a conversation about engagement is a good thing. For far too long, the focus has been on total fans. However, in order to gauge the value of this conclusion, let's first examine some possibilities why this is the case.

Fragmentation
The larger a community is , the more heterogeneous the make-up of its members. People fan brands for different reasons and at different points of entry. Some fans want product information or news, others are waiting for coupons or deals while there may also be a subset of you fan base that joined six months ago as a result of a contest or sweepstakes. Serving up relevant, engaging content to each of these constituencies can be a challenge. It was Abraham Lincoln who said "You can please most of the people some of the time, some of the people most of the time, but none of the people all of the time."

Globalization
Facebook's largest growth over the past year has come from users outside the United States. In fact, Facebook's fastest growing markets include Japan, Brazil and Bahrain -- with the U.S. not even cracking the top ten (source: CheckFacebook.com). It is only logical, then, that brand pages with larger fan totals have more international fans. Top brand pages typically post global status updates in one language, thus limiting opportunities for engagement per post by those who may like your brand, but do not speak that primary language.

Localization
The article also pointed out that half of all "likes" happen within 1 hour and 20 minutes of posting, and 70% happen within 4 hours. So if you're living in another time zone across the globe, the likelihood of engagement with global posts is greatly reduced. To reach local fans in a more impactful way, a number of the biggest brand communities are also delivering targeted messages to individual countries on a regular basis. Total engagement numbers on these localized posts will also be limited.

In defining "engagement" as likes and comments per post, the Visibli findings discount the value of clicks on links within posts as well. The same Buddy Media research they cite as a reference for publishing best practices indicates that messages with links outperform posts without links. And what about interactions with other content within the community, like photos, videos and inside page applications or experiences?

Does engagement matter?

While we have yet to collectively agree on a universal method for dollar value of a Facebook page, let's be sure that we're asking the right questions. There is no Klout score for a Facebook page, no universal scorecard to help understand the weight of qualitative and quantitative interactions. Total fans is not the answer, especially not the mythical "One Million Fan" target . Neither is the sum of likes and comments per post. These only tell part of the story.

A more holistic view of the community must look at four key areas in relation to each other over time.

• Reach: the number of fans a brand page is actually speaking with.
• Engagement: measuring how compelling a brand's News Feed presence is .
• Influence: Are you converting your Fans to take some sort of action?
• Attrition Score: Are your Fans sticking around?

Until we have a universal value index that everyone knows and understands, we will dance around the issue.

Of course, this still may not satisfy a brand manager looking to justify his or her social media budget to a CMO or COO. So if you put a gun to my head and asked me to tell you which metric matters most (and a few clients have come close), I would answer you with a KPI that Facebook does not currently make available through its Insights tool for page administrators. While Facebook measures Active Users (the total number of individuals -- fans or non-fans -- who interact with a brand's content), Facebook does not measure Active Fans. (Developers have said that they are working on it behind the scenes). Like unique page visitors of a website, a larger number of engaged fans is ultimately the goal of any community.

Meaning, of course, size still matters.