Ah, Morth, the Toes of a King are the Toes of a Healer
On the one hand you'd imagine many hundreds or a few thousand or so Dunedain, as only a small proportion would be Rangers (say 10%??). The majority must have been farmers, hunters, gatherers etc to feed the population. Also the Rangers must have suffered some casualties in the fight against the Nazgul at Sarn Ford, so reducing the number of available warriors.
On the other hand, Butterbur complained of the withdrawal of their protection and of course Sharkey and the Ruffians seem to have staged their Shire coup without any Rangerly interference. This points to there being very few Rangers left to help out.
Hmm, perhaps there were more Rangers than the famous 30-or-so, but could they have been busy with something else? eg. defending their strongholds from orc raids, the wolves west of the mountains, doing some scouting and messnger duties for the Brethren, or something else??