Eye Awareness & The Question of the Dunedain

[Tolwen]

Now there's a question! I think it would depend on when we hypothetically diverge from canon. If Arnor didn't split into it's successor kingdoms I'd speculate quite a high proportion would be Dunedain.
if the split happens but we avoid population collapse then I'd say Arthedain would have the highest proportion and Rhudaur by far the lowest with Cardolan being somewhere in between.

I can't see any support from Tolkien's writings that the Dúnedain ever were a major (let alone a majority) part of the population in the Realms-in-Exile. IMO it is quite the contrary: They were more likely a comparatively small caste of nobility ruling over a vast majority of "lesser" men.
This pertains to the "pure-blooded" Dúnedain of course. There would be a bigger (but still minority) number of mixed-blooded descent (where Dúnedain had intermarried with the indigenous or migrating edainic population). The latter would exhibit some traits of the Dúnedain to some degree but would not qualify as "Númenóreans/Dúnedain" in the closer sense.

I had some thoughts on this topic (number of Dúnedain in Middle-earth) in the Eriador article in OM13. perhaps that might help also somewhat. There is also a similar suggestion to the distribution of the "real" Dúnedain at the time of the split of Arnor into Arthedain, Cardolan and Rhudaur.

Cheers
Tolwen