This means that you've driven visitors to a product, but none of them have converted into a buying customer yet. Every product converts at a different rate, so there's no way to tell how many Hops it should take to make a sale.
However, if you're actively promoting a product (especially if you are spending money to promote a product), you should decide how many Hops you're willing to send to a product before you try a different strategy or product. Even if the product has converted for other people in the past, it may not convert for you.
Deciding when to stick with what you're doing and when to change course is an important part of testing and learning as an affiliate marketer.
ClickBank's Analytics tools can help you gather data on conversion rates, which may help you judge the effectiveness of your campaigns.
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