At first, Rod Buchignani just circled Facebook, eyeing it with curiosity, wondering if he should partake.
He joined last year, but the 64-year-old Northern Californian kept the social networking site at arm's length, thinking it belonged to younger generations.
"I wanted to get a flavor of what it was all about," he said. "It didn't appeal at the time, because there were a lot of younger people, and I didn't do too much with it."
My, how times have changed.
Now, about a year later, as more of his friends and family have joined, Buchignani shares photos, posts updates two or three times a week and regularly exchanges messages with other members.
"I feel like he's on it more than I am nowadays," said his 21-year-old daughter Claire.
Although it started as a college site, restricted to only those with ".edu" at the end of their e-mail addresses, Facebook has grown into a mammoth social mainstay. Facebook has publicly acknowledged that it has graduated well beyond its roots, revealing that the fastest-growing demographic is those 35 years old and older.
But new data suggest Facebook could be even more mature than previously believed.
According to the digital marketing firm iStrategyLabs, the number of users 55 years old and older grew about 500 percent in the last six months alone. Using demographic estimates disclosed by Facebook to advertisers, iStrategyLabs determined that the 55+ crowd could soon overtake high schoolers.
Out of the nearly 72 million Facebook members in the United States, as of July 4, the marketing firm said about 5.9 million are 55 years old or older, while about 7 million are 17 and younger. And in the same time period that saw remarkable growth for the oldest demographic, the youngest demographic grew by just 24 percent.
Peter Corbett, CEO of iStrategyLabs, acknowledged that part of staggering growth came from the fact that the older demographic started from a much smaller user base. But he believes the political and economic climate had a hand in propelling the growth.
"Facebook played such a large role in this election," Corbett said. Hearing it mentioned by news organizations, activists and party leaders time again likely led them to wonder, "What is this Facebook thing? Why is everyone talking about it?" he said.
"Then compound that with the economic environment," he said. People out of work might have felt the need to stay current while looking for opportunities, he said, and those still employed might have been compelled to stay connected with peers to secure a safety net of opportunities in case their luck changed.
As the demographics of Facebook shift, he pointed out, the dynamics of families, friend groups and work environments are shifting as well.
Aside from the estimates it provides to advertisers, Facebook does not publicize raw data on user demographics. And some have said that because user data fluctuate over time, comparing information from two dates doesn't necessarily present an accurate picture.
"Facebook has more than 200 million users around the world and we continue to see growth in all age segments, including people over age 55, in high school and college," Facebook spokeswoman Brandee Barker told ABCNews.com in an e-mail.
But other analysts say iStrategyLab's report is consistent with trends they've observed.