A group of bipartisan lawmakers sent letters to nine of the major data broker firms Wednesday asking the companies to explain how each collects, assembles and sells consumer information to third parties.

The companies — Acxiom, Epsilon (Alliance Data Systems), Equifax, Experian, Harte-Hanks, Intelius, Fair Isaac, Markle and Meredith Corp. — comprise some of the largest companies that have made a business by aggregating and selling personal information to other companies.

A group of lawmakers, including Congressional Bi-Partisan Privacy Caucus chairmen Reps. Ed Markey (D-Mass.) and Joe Barton (R-Tex.), have asked these companies to explain five things: where these companies get their information; what kind of data they collect; which companies buy the data; an explanation of how the data are protected; and an explanation of how consumers can get information on policies regarding how data are shared and deleted.

Lawmakers also asked for more information on how data brokers rank personal information and whether or not the companies collect information on minors.

The lawmakers said they were looking into the matter because many privacy advocates have “called for increased transparency by data brokers, including disclosure of their business practices and the rights consumers have over their own personal information.”

The Federal Trade Commission has also called for a transparency law for Internet data brokers, as The Washington Post reported in March.

Other signatories on the letter include Reps. Henry A. Waxman (D-Calif.), Steve Chabot (R-Ohio), G.K. Butterfield (D-N.C.), Austin Scott (R-Ga.), Bobby Rush (D-Ill.), and Jan Schakowsky (D-Ill.)