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An information broker (independent information professional, information consultant) collects and sells information. Uses include targeted ads, market research, consumer scoring, patent searches, and election campaigns. The industry has been criticized for being unregulated and opaque.
The internet has caused a dramatic expansion in individual data; one broker, Acxiom, claims to have files on 10% of the world's population, with about 1500 pieces of information per consumer. Individuals generally cannot find out what data a broker holds on them, how a broker got it, or how it is used.
Files on individuals are generally sold in lists; examples cited in testimony to the U.S. Congress include lists of rape victims, seniors with dementia, financially vulnerable people, people with HIV, and police officers (by home address). Less controversial are lists of rich people, doctors, or parents.
There are probably between 3500 and 4000 data broker companies, and about a third may provide opt-outs, with some charging over a thousand dollars for them.
Credit scores were first used in the 1950s, but did not become widely known or specifically regulated until the 1990s.
In 1977 Kelly Warnken published the first fee-based information directory, which continues to be published and has expanded to cover international concerns.
The Association of Independent Information Professionals, the first professional association devoted to information brokers, was formed in Milwaukee in 1987. The profession has its roots in 1937 when librarians and other information professionals formed an organization called the American Society for Information Science and Technology in an attempt to establish their professional identity separate from public libraries.
A U.S. Senate Committee published A Review of the Data Broker Industry: Collection, Use, and Sale of Consumer Data for Marketing Purposes. It states that "Today, a wide range of companies known as “data brokers” collect and maintain data on hundreds of millions of consumers, which they analyze, package, and sell generally without consumer permission or input." Their main findings were that:
- Data brokers collect a huge volume of detailed information on hundreds of millions of consumers.
- Data brokers sell products that identify financially vulnerable consumers.
- Data broker products provide information about consumer offline behavior to tailor online outreach by marketers.
- Data brokers operate behind a veil of secrecy.
The U.S. Federal Trade Commission published "Protecting Consumer Privacy in an Era of Rapid Change" in March 2012, advising businesses and consumers on the protection of privacy, data and digital security. The document recommended that Congress "consider enacting targeted legislation to provide greater transparency for, and control over, the practices of information brokers." It noted a "lack of transparency about the practices of information brokers, who often buy, compile, and sell a wealth of highly personal information about consumers," unbeknownst to them. Finding that consumers are "often unaware of the existence of these entities, as well as the purposes for which they collect and use data," the report recommended legislation giving consumers more knowledge of and control over information brokers' use of their data.
An Online Information Broker FAQ is published by Privacy Rights Clearinghouse (PRC), a nonprofit consumer organization in the United States. PRC also maintains a list of information brokers, with links to their privacy policies, terms of service, and opt-out privisions.
Data brokers have also faced legal charges for security breaches due to poor data security practices 
The Data Accountability and Trust Act contained a number of requirements for auditing and verification of accuracy of data held by information brokers, and additional measures in the case of a security breach. The bill also gave identified individuals the means and opportunity to review and correct the data held that related to them. It passed through the United States House of Representatives in the 111th Congress, but failed to pass the United States Senate. It was revived by the 112th Congress in 2011 as H.R. 1707., but died after being referred to committee. The bill was first introduced by Rep. Bobby Rush [D-IL1] on Apr 30, 2009, H.R. 2221
A Master's degree in library science (M.L.S.) or in library and information science (M.L.I.S.) is preferred or the norm. However, these prerequisites aren't always necessary. Some brokers have a master's or PH.D in law, social sciences or liberal arts.
In fiction, information brokers usually find data for a story's main character(s). Fictional information brokers can be of varying importance and have varying methods. For example, a hacker can be an information broker, though they may be simply transferring whatever information they find to the main character(s). Other brokers may have memorized data and tell the main character(s) covertly. Also, a fee is not always involved. The information broker may have an alliance with the main character(s) or be one themselves.
Examples of information brokers in contemporary fiction would be DC Comics' superheroine, the Oracle; Edward G. Robinson's character Sol in the film Soylent Green; the Shadow Broker in the video game series Mass Effect; Nicholas Wayne, Rachel, Elean Duga, Gustav St. Germain, Carol, and the President of the Daily Days newspaper company in Baccano!; or Izaya Orihara in the light novel series Durarara!!.
- Carvell, Linda P. (2005). Career Opportunities in Library and Information Science. New York: Checkmark Books. pp. 75–79, 171–181.
- Taylor, Allen and James Robert Parish (2009). Career Opportunities in Library and Information Science. New York: Ferguson. pp. 206–212.
- http://www.nytimes.com/2012/06/17/technology/acxiom-the-quiet-giant-of-consumer-database-marketing.html, quoted in http://www.commerce.senate.gov/public/?a=Files.Serve&File_id=0d2b3642-6221-4888-a631-08f2f255b577
- Online Information Broker FAQ | Privacy Rights Clearinghouse. Privacyrights.org (2010-10-04). Retrieved on 2014-05-06.
- Privacy Rights Clearinghouse. Privacyrights.org (2004-10-01). Retrieved on 2013-11-12.
- Data Accountability and Trust Act (2011; 112th Congress H.R. 1707). GovTrack.us. Retrieved on 2013-11-12.
- Data Accountability and Trust Act (2009; 111th Congress H.R. 2221). GovTrack.us. Retrieved on 2013-11-12.
- "TC Recommends Congress Require the Data Broker Industry to be More Transparent and Give Consumers Greater Control Over Their Personal Information". Federal Trade Commission. Retrieved 31 May 2014.