The growth in usage also hasn't been enough to put Google+ within the top 10 sites in Experian Hitwise's Social Networking and Forums category, in which it ranked 13th as of last week.

Still, the trend is encouraging, according to Experian Hitwise spokesman Matt Tatham. "The site is doing well," he told IDG News Service in a phone interview. "It's down from the [September one-week] peak but it's considerably higher than where it was."

Compared with the first four weeks of September, total visits to Google+ rose 30 percent during the same period in October, when the site attracted an average of 6 million total visits per week, he said.

Total page views climbed 37 percent, as the site averaged about 15 million page views per week, and time spent on the site rose 5 percent, according to Experian Hitwise. Its data is limited to the U.S. and doesn't include mobile traffic or traffic from the Google+ notification bar.

Also positive is that Google+ has had an average percentage of returning visitors of 62 percent since it launched in limited beta in late June, which Tatham considers a good level of repeat activity.