In February 2000, Amazon announced that it had been granted a patent[18] on components of an affiliate program. The patent application was submitted in June 1997, which predates most affiliate programs, but not PC Flowers & Gifts.com (October 1994), AutoWeb.com (October 1995), Kbkids.com/BrainPlay.com (January 1996), EPage (April 1996), and several others.[13]
Cost per mille requires only that the publisher make the advertising available on his or her website and display it to the page visitors in order to receive a commission. Pay per click requires one additional step in the conversion process to generate revenue for the publisher: A visitor must not only be made aware of the advertisement but must also click on the advertisement to visit the advertiser's website.

A successful customer referral program can become the lifeblood of your business, but it won’t do anything if it’s not backed by the proper resources. The program should be strategically planned out, regularly measured, and managed on an ongoing basis. When you invest in your program, you can see unimaginable growth through this marketing channel (just look at the ROI of referral marketing by different industries). You can’t achieve success if you’re treating your referral program as an afterthought. Successful programs need structure and commitment from within your company. For this reason, many brands choose automated and streamlined platforms to ensure ease and satisfaction from both a consumer and company perspective.
You may use both cash or non-cash incentives for referral marketing example, but a Chicago University study found that non-monetary incentives were more effective than cash benefits by 24%. It is also better to not confine referral to customers or employees alone, referral marketing websites can also be used to new customers and lure them into referral marketing programs. 
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