agent who arranges for the rental of lists by a list user on behalf of the list owner in return for a commission on the rental fee. List brokers perform various marketing and list consultation services in the process of bringing buyer and seller together, such as researching and recommending lists to the list user and evaluating the performance of each list after mailing. List brokers are also responsible for controlling on-time delivery of the list to the list user and usually guarantee payment for the list rental to the owner. A list broker may work exclusively with a house list or with several compiled list or lists geared to specific target markets such as people over sixty, homemakers, or executives.