Source: Concept from negotiation analysis, closely associated with Howard Raiffa, The Art and Science of Negotiation
The Zone Of Possible Agreement is the overlap between the lowest you will accept and the most the other side will pay. A deal is only possible if that overlap exists.
When to use it
Use it to judge whether a deal is realistic and where to aim within the range.
How to apply it
Set your walk-away figure using your BATNA.
Research the likely employer range using job adverts, recruiters and salary surveys.
Estimate the other side's maximum, considering pay bands and recruitment costs.
Map both ranges and identify the overlap.
Aim your opening towards the top end of the overlap, backed by evidence.
Tip: If there is no overlap on salary, widen the deal to other terms rather than giving up immediately.