Google announced the addition of +1 button data to Google Analytics and Webmaster Tools. These new metrics can show you how the +1 button actually affects the traffic to your site.
In WMT, there is a Search Impact report, which shows how +1's affect your organic search traffic. "You can find out if your clickthrough rate changes when personalized recommendations help your content stand out," says Google software engineer Dan Rodney. "Do this by comparing clicks and impressions on search results with and without +1 annotations. We’ll only show statistics on clickthrough rate changes when you have enough impressions for a meaningful comparison."
An Activity report shows how many times your pages have been +1'd, from buttons on your site, as well as on other pages like Google Search.
An Audience report will show you aggregate geographic and demographic data about who is using the +1 button with your content. Google only shows this info, however, when a "significant" number of users have +1'd pages. They don't say what number they consider "significant" to be.
Users will find a +1 Metrics menu on the side of the page, where each of these reports will be able to be found.
Google is also showing how users share content using other buttons with Social Plugin Tracking in Google Analytics. This includes a Social Engagement report, which shows how site behavior changes for visits that include clicks on +1 buttons and other social buttons. "This allows you to determine, for example, whether people who +1 your pages during a visit are likely to spend more time on your site than people who don’t," says Rodney.
Also included are the Social Actions report, which tracks the number of social actions taken on your site, and the Social Pages report, which lets you compare pages on your site to see which are driving the most social actions.
"Over the next few days (and if you’re using the default version of the latest Google Analytics tracking code), if you’ve added +1 buttons to your site we’ll automatically enable Social Plugin Tracking for +1 in your account," Rodney says. "You can enable tracking for other social plugins in just a few simple steps."