Unless you pay for it, it's unlikely your brand's message is going to reach a critical mass of people on Facebook.

That's because organic reach -- which Facebook defines as “the number of unique people who saw your post in News Feed or on your page" and marketers recognize as essentially free advertising —has taken a nosedive.

Two years ago, Facebook page posts reached 16 percent of a brand's fans organically, according to Facebook. As of this February, an analysis by Ogilvy & Mather put that number at 6 percent. "Organic reach of the content of brands is destined to hit zero," the analysis prophesized. "It's only a matter of time."

Not a bad prediction; In March, reports surfaced that Facebook was cutting organic page reach down even further, from 6 percent to a miserly 1 to 2 percent.

Related: Best Practices for Businesses Using Facebook

A common theory was that Facebook was slashing organic reach in order to squeeze more money out of advertisers. In March, online food ordering service Eat24 summarized the discontent many brands felt about the changes in a blog post explaining why it was ditching Facebook for good.  "When we first met, you made us feel special," the post read. "We’d tell you a super funny joke about Sriracha and you’d tell all our friends and then everyone would laugh together. But now? Now you want us to give you money if we want to talk to our friends."

In a blog post of its own published yesterday, Facebook finally responded to these criticisms, denying that organic reach's decline on its site has anything to do with making money. Instead, the company said, it's a natural response to the explosion of content that gets published on its network.  "On average, there are 1,500 stories that could appear in a person’s News Feed each time they log onto Facebook," Brain Boland, Facebook's ad product marketing lead, wrote in the post. "As a result, competition in News Feed — the place on Facebook where people view content from their family and friends, as well as businesses — is increasing, and it’s becoming harder for any story to gain exposure in News Feed."

Related: Is Facebook Really a Failure to Marketers?

To handle the onslaught of content, Facebook says it has updated the News Feed so that it only shows individuals the content that is most relevant to them. According to Boland, Facebook ranks the more than 1,500 stories a person could see when they log on to Facebook from more to less important "by looking at thousands of factors relative to each person." Three-hundred or so of the most relevant stories are selected and displayed.

While Facebook claims that organic reach's decline isn't motivated by a desire to rack in the cash, that will undoubtedly be the end result.

A brand's fans are still valuable, after all. " When an ad has social context — in other words, when a person sees their friend likes your business — your ads drive, on average, 50% more recall and 35% higher online sales lift," Boland writes. Now, however, marketers will have to pay to reach them.

Related: Why Your Facebook Page Is Becoming Less Relevant

In the post, under the sub-head "How do I use Facebook for my business?" Boland recommends ponying up:

"Like TV, search, newspapers, radio and virtually every other marketing platform, Facebook is far more effective when businesses use paid media to help meet their goals. Your business won’t always appear on the first page of a search result unless you’re paying to be part of that space. Similarly, paid media on Facebook allows businesses to reach broader audiences more predictably, and with much greater accuracy than organic content."