Update: As the study has generated some confusion, I'm going to repost the author's explanation (which also appears in the comments) here:
This study, which measures the CTR of different social network users, was conducted using a referrer based methodology.
When we discuss referrer, we mean it in this way:
Let’s say, for example, harold.com is a publisher on the Chitika network (aka a person who runs Chitika ads). If, for example, someone on Google+ posts a link that leads to a particular page on harold.com, the person clicking this link would be said to be referred to harold.com by plus.google.com.
What we are measuring is the CTR on harold.com from plus.google.com referrals, not plus.google.com itself. To simplify, we are measuring the CTR of generated traffic, not of the website.
Obviously this is a small sample, so the study in question measured the CTR of all publisher sites included within our study when the referrer was Google+, Facebook, and Twitter. This is similar to the methodology Chitika used in our first major research study, measuring the CTR of traffic generated from Google, Yahoo, and Bing (link: http://insights.chitika.com/2009/clickthrough-rate-analysis-bing-vs-google-vs-yahoo/ ).
To summarize, the CTR in question is calculated as (# of clicks generated from impression set) / (# of impressions received on a publisher webpage from a link posted on Google+/Facebook/Twitter). Hope this helps.
“Given the announcements and roll out of new social media advertising programs on platforms including; Google+, Facebook and Twitter, we wanted to investigate where advertisers will have the highest potential to engage with users based on CTR (Click Through Rate),” a representative for Chitika tells WebProNews. “To quantify this study, we analyzed a sample of data from the extensive Chitika ad network, covering hundreds of millions of impressions, to compile a data set which yielded the CTR (Click Through Rate, or likelihood of a user clicking on an ad) of the average user on the three social networks.”
The firm isolated the referrer domain for Google+, Twitter and Facebook, to compile a data set which yielded clickthrough rate of the average user on each social network.
Google+ and Twitter users click on ads with about the same frequency, according to Chitika’s findings.
Facebook measured a .24% CTR, while Google+ and Twitter users ranked at .1 and .09% respectively.
“As always, a cost-benefit analysis is key to identifying which platform (if any) is worthwhile for your product or service,” Chitika says. “One of the biggest factors in deciding which form of social network advertising is the best choice is highly dependent on the type of campaign being run. For instance, in marketing a time sensitive campaign, utilizing an analytical approach with Twitter’s promoted trends could be more effective than pursuing standard Facebook ads. Moreover, it is possible as a marketer to optimize for all segments of traffic, and when making the final decision on an ad campaign, it is essential to keep your target market in mind.”