Twelve years ago Thursday, Mark Zuckerberg founded Facebook with a simple dream: to have everyone spending as much time as possible clicking around on his website. Today, the social network site's users are closing in on $3.5 trillion in squandered productivity.

The company has about 1.6 billion monthly active users, more than the population of any single country on earth. And those users are valuable — Facebook makes an average of $3.73 in revenue per user worldwide (and much more for Americans), according to quarterly results reported last week. By market cap, each of those users is worth more than $200 in valuation.

Facebook's users spend an aggregate of 10.5 billion minutes per day on the platform (excluding mobile), according to the company's 2012 IPO filings. And engagement — based on the number of monthly users who visit the site daily — is even higher today.

Assuming that users spend about the same amount of time today, that means people all over the world have spent a collective 55 million years on Facebook since the beginning of 2009.

Twenty minutes a day is a lot of time — well more than a year over the course of the average life span. If users spent just that time working for minimum wage instead of liking and poking each other, each would pull in about $880 a year. That's almost $900 billion in aggregate hypothetical labor last year.