I did a survey of this some years ago. I don't have the results any more, but my recollection is of a very wide (20kgish) range of masses used by various operators - there doesn't seem to be much of a standard.
Equally worrying is that the airworthiness standards for big jets are only using around 77kg per seat to determine crashworthiness. To my mind, ludicrously low. (Pilot seats use 86kg, which is a little better, but still frankly too low.)
G