Question: One thing that confuses me is that on a few products, the refund rate says 'na', while on the rest it always shows a percentage (even when it's a new product, and the rate is 0%)

What does the 'na' signify?

Answer: NA signifies NOT AVAILABLE. We are unable to calculate return rates for recurring products and vendors with multiple product IDs. Keep in mind, refund rates are not an exact science. We simply subtract the payout from the average earned to get a percentage. Occasionally vendors change product prices which will skew return rate percentages.  We're hoping in the future Clickbank makes precise return rate data available.

Matt