The Camarata book has various related facts & figures (especially at the beginning of chapter 2) although I don’t recall him saying the exact thing you’re looking for.
If you have a specific child in mind, then you have much much more information about them than “they are non-verbal or minimally-verbal at age X”. You (hopefully) know whether or not they’re hearing-impaired, and you hopefully know whether or not they have Down’s syndrome, and you hopefully know whether or not they have other other indications of severe autism, and you hopefully know something about their receptive language and social pragmatics, etc. So I’m not sure that the population statistics would be all that useful. (Unless the study population is a decent match to what’s known about the kid, I guess.)
The Camarata book has various related facts & figures (especially at the beginning of chapter 2) although I don’t recall him saying the exact thing you’re looking for.
If you have a specific child in mind, then you have much much more information about them than “they are non-verbal or minimally-verbal at age X”. You (hopefully) know whether or not they’re hearing-impaired, and you hopefully know whether or not they have Down’s syndrome, and you hopefully know whether or not they have other other indications of severe autism, and you hopefully know something about their receptive language and social pragmatics, etc. So I’m not sure that the population statistics would be all that useful. (Unless the study population is a decent match to what’s known about the kid, I guess.)