|Headquarters||San Francisco, California, United States|
|Key people||Joe Fernandez (CEO)
Emil Michael (COO)
|Slogan(s)||The Standard for Influence|
|Alexa rank||845 (December 2013[update])|
|Type of site||Social Networking|
Klout is a website and mobile app that uses social media analytics to rank its users according to online social influence via the "Klout Score", which is a numerical value between 1 and 100. In determining the user score, Klout measures the size of a user's social media network and correlates the content created to measure how other users interact with that content.
Klout utilizes Twitter, Facebook, Google+, LinkedIn, Foursquare, Wikipedia, and Instagram data to create Klout user profiles that are assigned a unique "Klout Score." Klout scores range from 1 to 100, with higher scores corresponding to a higher ranking of the breadth and strength of one's online social influence. While all Twitter users are assigned a score, users who register at Klout can link multiple social networks, of which network data is then aggregated to influence the user's Klout Score.
Klout measures influence by using data points from Twitter, such as following count, follower count, retweets, list memberships, how many spam/dead accounts are following you, how influential the people who retweet you are and unique mentions. This information is blended with data from a number of other social network followings and interactions to come up with the Klout Score. The social networks that influence a user's Klout Score are Twitter, Facebook, Google+, LinkedIn, Instagram and Klout itself, as well as Wikipedia. Other accounts such as YouTube, Flickr, Blogger, Tumblr, Last.fm, WordPress, and Bing can also be linked by users, however they do not weigh into the Klout Score as of March 2013[update]. Microsoft announced a strategic investment in Klout in September 2012 whereby Bing would have access to Klout influence technology, and Klout would have access to Bing search data for its scoring algorithm.
Klout scores are supplemented with three nominally more specific measures, which Klout calls "true reach," "amplification" and "network impact." True reach is based on the size of a user's engaged audience who actively engage in the user's messages. Amplification score relates to the likelihood that one's messages will generate actions, such as retweets, mentions, likes and comments. Network impact reflects the computed influence value of a person's engaged audience.
The primary business model for Klout involves brands working with Klout through Perks campaigns. In a Perks campaign, a brand will offer free experiences or products to Klout users who match a pre-defined set of criteria including their scores, topics, and geographic locations. While Klout users who receive Perks are under no obligation to create content about the Perks they have received, brands that participate in these campaigns do so with the intent of generating content that will then be shared in social media channels. Klout has offered the Perks program since 2010. According to Klout CEO Joe Fernandez, about 50 of partnerships had been established as of November 2011. In May 2013, Klout announced that its users had claimed more than 1 million Perks across over 400 campaigns. 
Klout for business
In March 2013, Klout announced its intention to begin displaying business analytics aimed at helping business and brand users learn about their online audiences.
Several objections to Klout's methodology have been raised regarding both the process by which scores are generated, and the overall societal effect. Critics have pointed out that Klout scores are not representative of the influence a person really has, highlighted by Barack Obama, President of the United States, having a lower influence score than a number of bloggers. Other social critics argue that the Klout score devalues authentic online communication and promotes social ranking and stratification by trying to quantify human interaction. Klout has attempted to address some of these criticisms; a recent update to Klout's algorithms does now rank the importance of Barack Obama in a way that more reflects perception.
The site has been criticized for violating the privacy of minors, and for exploiting users for its own profit.
John Scalzi has described the principle behind Klout's operation as "socially evil" in its exploitation of its users' status anxiety. Charles Stross has described the service as "the Internet equivalent of herpes," blogging that his analysis of Klout's terms and conditions reveals that the company's business model is illegal in the United Kingdom, where it conflicts with the Data Protection Act 1998; Stross advises readers to delete their Klout accounts and opt out of Klout services.
Ben Rothke concluded that "Klout has its work cut out and it seems like they need to be in beta a while longer. Klout can and should be applauded for trying to measure this monstrosity called social influence; but their results of influence should in truth, carry very little influence." 
- September 2011: Klout integrates with Google+
- October 2011: Klout changes its scoring algorithm lowering many scores and creating complaints
- November 2011: Klout partners with Wahooly for their beta launch
- January 2012: Klout was able to raise an estimated $30 million from a host of venture capital firms.
- February 2012: Klout acquires local and mobile neighborhood app Blockboard.
- May 2012: Klout announces growth of 2000 new partners over a one year period. 
- August 14, 2012: Klout went through another algorithm change.
- September 2012: Microsoft announces a strategic investment in Klout for an undisclosed sum.
- March 28, 2013: Klout announces inclusion of Instagram analytics in factoring Klout scores.
- May 13, 2013: Klout users had claimed more than 1 million Perks across over 400 campaigns.
- Q Score, a rating system for brand/celebrity popularity
- Bugscore, a rating system for people, brand, product popularity
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