The affiliate marketing industry is in the midst of rapid growth. A Forrester Research 2003 study found more than half of online retailers were using affiliate programs -- and 99 percent of them said the tactic was effective at driving sales. That finding outstrips the approval ratings for email, search marketing and portal deals. In addition, affiliate programs generally can attain between 10 to 30 percent of a brand’s total online transactions over time. According to the 2003 Affstat Report, of active affiliate programs, 18 percent are driving 30 percent or more of total site transactions.