How to view your +1 stats in Google Webmaster Tools
To view the data regarding the Plus One clicks your site receives it must be registered with Google Webmaster Tools and verified. To see your stats select the web site under consideration and expand the +1 Metrics menu in the left pane. There you find the three submenu items Search Impact, Activity and Audience.
The Search Impact report tells you whether and how the plus one button affects your traffic from the Google Search Engine and personalized information if you have been plus oned by people your are related with through your Google account, such as your contact list or Gmail for example. You can compare annotated clicks, annotated impressions, all impressions or all clicks against Click-Through-Rate (CTR), impressions and clicks.
Depiction of +1 button search impact:
Image source: Google Webmaster Central Blog
The Activity report graphically displays new +1's, or the sum of all +1’s for the URL under consideration. On the Activity page you also find out about the origin of the plus ones, which can be coming from your own pages, or from users who've +1ed your URL on search engine results and advertising.
Finally, the Audience report tells you about the number of unique users who have hit the Plus One button, as well as their age, gender and location, similar to Google Analytics stats. Note that some activity and audience stats are only displayed after Google has gathered enough meaningful information and privacy issues are no longer a concern, both of which are based on having enough people +1 your content.