An ad relevance diagnostic showing how an ad's conversion rate compares to ads with the same optimization goal competing for the same audience. Possible values are ranks like BELOW_AVERAGE_20, AVERAGE, ABOVE_AVERAGE_10, etc. It only applies at the ad level (not to campaigns or ad sets). A rank of ABOVE_AVERAGE means the ad's conversion rate is better than most similar ads.
This appears in insights when requesting conversion_rate_ranking.
