Ask HN: Online affiliate marketing industry size?

Does anyone know of any figures for how much money is made online by affiliate marketers for sites like amazon, ebay, etc.

I'm looking to get an estimate for how much has been paid out through programs like these, and also any specific examples of entire businesses being supported by affiliate revenue?

Anytime I try to look for this type of info I'm instead barraged with "How to make money as an affiliate marketer" click bait.

Thanks for any responses/insights.