Sorry, I didn't mix up anything. (Passenger) yield is revenue per RPK. Check out IATA stats, or AEA, or AAPA. I work with this stuff every day, it has paid my salary for the last 40+ years.
'Revenue per seat' or 'revenue per passenger' is parochial. It allows you to compare within an airline with a single product, or on a single route. To compare across the networks you can only look at RPK/ATK.