Both Uses

scarcity
in
Pride and Prejudice
(Auto-generated)

Elizabeth Bennet had been obliged, by the scarcity of gentlemen, to sit down for two dances; and during part of that time, Mr. Darcy had been standing near enough for her to hear a conversation between him and Mr. Bingley, who came from the dance for a few minutes, to press his friend to join it.†
p. 13.3 *

scarcity = shortage (having an amount that is less than desired)
He danced only four dances, though gentlemen were scarce; and, to my certain knowledge, more than one young lady was sitting down in want of a partner.†
p. 170.9

scarce = in short supply OR barely or hardly (by a small margin)

Definitions:

(1) (scarcity)
shortage (having an amount that is less than desired)
(2) (meaning too rare to warrant focus)
More rarely (and typically in classic literature), scarce can be short for scarcely or hardly or barely or by a small margin -- such as in "She was scarce ten years old," or "I scarce know why."