TORONTO - Privacy concerns don't seem to have scared Canadians off Facebook.

Canada passed the 16 million users mark in May, according to research firm Inside Network.

An estimated 912,380 Canadians signed up for the site last month, a six per cent increase in membership.

That spike came at the same time that two Toronto residents promoted the idea of Quit Facebook Day on May 31. The campaign drew pledges to leave Facebook from almost 36,000 users worldwide, but most simply shrugged and went back to posting status updates.

An estimated 47.9 per cent of Canadians are on Facebook, making Canada one of the most plugged-in countries in the world, said Justin Smith, founder of Inside Network.

While Facebook does not issue specific membership numbers, Inside Network uses data provided to advertisers to gather insights about the social networking site.

Overall, Canada is the fourth largest market on Facebook, on a per capita basis, behind Iceland, Norway and Hong Kong. About 59.6 per cent of Iceland's population has a Facebook profile.

But among larger countries with at least 10 million citizens, Canada is No. 1, Smith said.

"Canada is pretty persistently the top country of any reasonable size that has achieved this level of Facebook penetration," he said.

"Because Canada has been such a strong early adopter, these days they're not leading by growth rate -- because there's only so much more you can actually grow."

There has been speculation recently that Facebook is approaching 500 million users worldwide, although it has only officially stated it has more than 400 million users.

Facebook now has about 465 million users in total, according to Inside Network's latest report, and may be a few weeks or months away from hitting the half-billion mark.

Facebook has averaged about 500,000 new users daily for the last year but spiked in May with about 30 million new members, Smith said.

"Facebook has grown very rapidly, very quickly in unprecedented form," he said.

"There are dozens and dozens of countries where 30 to 40 per cent of the entire population is accessing Facebook at least every month. To me that reflects a pretty big shift in the way people are sharing information online and how Facebook is affecting culture."

In terms of the fastest growing countries in May, Iraq led the pack, followed by South Korea, Nigeria, Thailand and Guatemala.