Google+ continues to struggle building a significant user base in the United States. According to new data published by GlobalWebIndex , there are 14 million active Google+ users in the U.S.With a penetration rate of only 6 percent, Google+ remains far behind its competitors Twitter and most importantly Facebook, which has a penetration rate way beyond 50 percent of U.S. Internet users.In other developed economies Google+ faces the same difficulties: With penetration rates of 4, 5 and 7 percent in Germany, Japan and the United Kingdom respectively, Google+ remains a niche service in these countries.On a positive note, Google appears to be making headway in emerging economies. Google+ is used by at least 25 percent of Internet users in all four BRIC nations; India standing out with a penetration rate of 38 percent.Above chart shows the penetration rate of Google+ in selected countries.