Concessions
a - our offer,
b - opponent’s offer
a1 - new offer yielding a concession (utility level drops from U0 to U1),
Opponent does not reply and we propose a2. In terms of the distance in the offer space a2 is closer to b than a1 which is closer than a.
Search for a compromise without making
What one considers a concession may not be
an improvement for one’s opponent.