Today's Chart of the Day demonstrates just how quickly Google+ has grown since its launch on June 18. It compares the amount of time it took each of the three major social networks to reach 10 million users. (We can call Facebook, Twitter, and Google+ the Big Three now, right? Just like the Big Three in the American auto industry or the Miami Heat.) The chart has been making its rounds across the Internet today since its creator, Leon Håland, uploaded it on Google+ (of course). It only took 16 days for the nascent social network to sign up 10 million users, which is approximately 50 times faster than Twitter's or Facebook's dash to that mark.

A tech research company says Google+ already has 20 million users. The speedy growth of Google+ makes sense given its decent 7 percent share of the email client market and the ease with which any Gmail user can join the network. We venture to guess that Gmail tends to attach the savvy sort of Web users that become early adopters of new sites. In any case, Google+ has to maintain its rapid expansion if it's to succeed where Wave and Buzz failed. And consider: 10 million users is a drop in the bucket compared to Facebook's 750 million.

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