Well there are biases also, first and foremost that this data is from Indeed.com and I doubt most high quality CTO positions are posted there. It would definitely make sense to separate based on company size for executive positions.
Even the custom reports we get are "wrong" if you don't slice the statistics correctly. And a lot of people have no idea what's going on with compensation (salary, bonus and equity) right now, in competitive markets and competitive fields.
Our company is only 700 people and it's been a huge challenge.