Map the likely ZOPA before the first session

Estimate both your own and the counterpart’s reservation points before you open, so you know what deal space exists.

Why it works

Entering a negotiation without a ZOPA estimate is like navigating without a map: you can’t tell whether an agreement is within reach or whether your proposals are inside or outside the zone. The estimation forces you to think from both sides, which itself reduces the "fixed-pie" bias — the common assumption that the counterpart’s gain is your loss.

How to do it

1. Write your reservation price (the worst deal you would accept over no deal).
2. Estimate the counterpart’s reservation price — the worst they would take. Use market data, public information, and inference from their situation.
3. If your reservation prices overlap, a ZOPA exists. Note the range.
4. Set your opening position inside or near the top of the ZOPA for the other side — ambitious but plausible.

Evidence

ZOPA mapping is foundational negotiation analysis with strong practitioner and case-study support. Research on "fixed-pie" bias — which ZOPA analysis directly counteracts — is well-documented experimentally. (observational)

ZOPA estimation depends on accurate information about both sides’ alternatives — information that is often incomplete. Treat initial estimates as working hypotheses, not certainties.

Sources

• Thompson & Hastie (1990), "Social perception in negotiation", Organizational Behavior and Human Decision Processes

Common mistake

Mapping only your own side of the deal space and treating the counterpart’s position as opaque — this leaves half the information needed to navigate the zone.