The number of unique visitors to the global social networking sites reached 945 million in July, 23 percent higher than the same month last year, according to market researcher comScore.

The U.S. remained the largest social networking market with 174 million unique visitors in July, 33 percent up from a year ago. It was followed by China with 97 million visitors.

Russia registered the highest percentage growth in unique visitors at 74 percent or 35 million in July. It was followed by South Korea, which had 25 million visitors in July, 57 percent up from last year's figure of 16 million visitors.

Germany's social networking users grew 47 percent or 38 million in July to rank third and Brazil was at fourth with 35 million visitors. India's social networking sites visitors grew 43 percent to 33 million and Japan-based users expanded 35 percent to 32 million.

The growth of social networking sites users is being attributed to more older people joining Facebook, Twitter and the like. A Pew Research Center (PRC) report supported this observation.

About 26 percent of social network users aged 65 years old and older used such sites in March, up 22 percent from November 2008, according to PRC. Those aged 50 to 64 comprised 31 percent of users in March, 47 percent up from November 2008.