57% of online shoppers say they are more likely to purchase a product they see advertised on multiple web sites than if the same product were displayed only on retailer or brand sites, according to a new study from Forrester Consulting, a unit of Forrester Research Inc.

In addition, 48% of online shoppers say the promotional offers they find on coupon sites, blogs or other non-retailer affiliate marketing sites are often more valuable than the promotional offers they get directly from a retailer or brand site, the study adds.

With that kind of strong consumer response to affiliate marketing—which involves the use of paid listings on affiliate sites like coupon sites and blogs to direct online consumers to retailers’ sites—online merchants are planning to increase their spending on affiliate marketing by 16.6% per year over the next several years, from $2.08 billion in 2011 to $4.47 billion in 2016, the study says.

The study, “Affiliate Marketing–The Direct and Indirect Value that Affiliates Deliver to Advertisers,” was conducted in April and commissioned by Rakuten LinkShare Corp., a unit of Rakuten Inc. that operates a network of affiliate marketing web sites and other online marketing services. The study was based on a survey of more than 500 U.S.-based online buyers and several interviews with advertisers and operators of affiliate marketing sites.

The study also noted the following:

42% of online buyers who had made four or more purchases after responding to an affiliate ad said they were likely to try a new brand after seeing an offer on a non-retailer site.

52% of online buyers said they’d be willing to reconsider a brand they hadn’t used in a while after receiving a promotional offer from a non-retailer web site.

43% of online buyers said that promotional offers they find on affiliate marketing sites often help them decide to make a purchase.

74% of online buyers said they research two to three non-retailer web sites before completing a purchase decision.

65% of online buyers said they find it easier to find what they’re looking for on sites that feature products from multiple retailers or brands, compared with sites that feature only one retailer or brand.

Rakuten is the parent company of Buy.com, No. 36 in the Internet Retailer Top 500.

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