Google Inc. (Nasdaq: GOOG)’s new social-networking service may grow to claim 22 percent of online U.S. adults in a year, passing Twitter Inc. and LinkedIn Corp. (NYSE: LNKD) to be the second- most-used social site after Facebook Inc., a survey found.

Google+ has signed up 13 percent of U.S. adults and will add 9 percent over the next year, according to the survey from Bloomberg/YouGov. In the same period, Facebook will lose about 2 percentage points of U.S. adults to keep 69 percent of that population, while Twitter and LinkedIn continue to grow their portion of users.

Started in late June, Google+ is growing faster than Facebook and MySpace Inc. did in their early days. The service, which lets people connect with and manage groups of friends on a website, gained about 25 million users worldwide in less than a month, estimates market researcher ComScore Inc. (Nasdaq: SCOR) Facebook has more than 750 million active users.

“Google+ is tracing a path similar to Facebook’s initial growth — building excitement in a core group of early adopters,” said Michael Nardis, head of YouGov investment products, in a statement about the survey.

Bloomberg and London-based market researcher YouGov Plc (YOU) polled 1,003 online U.S. residents 18 and older from July 29 to Aug. 2 for the survey.

The results showed Twitter will add almost 3 percentage points of U.S. adults online over the next year to claim 20 percent of the population. LinkedIn will also have signed up 20 percent of those people, after gaining almost 2 percentage points within the year, the survey found.

Networking Every Day

Among survey respondents who had signed up for Google+, 45 percent said they read content on the site every day, compared with Facebook’s 62 percent of users. Twitter has 42 percent of its users return daily, while LinkedIn has 8 percent.

Google+ usage is likely to take away from the time people spend on Facebook, the survey found. Some 30 percent of people who use both services said they plan to reduce the amount of time they spend on Facebook.

Some 31 percent of Google+ users polled said they have already abandoned their accounts or not written any posts yet on the site.

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