Die «Zone of Possible Agreement» (ZOPA) describes the space in which agreement is possible, i.e. the space between your maximum target and your walk-away position. The larger the ZOPA on both sides, the more room there is for coming to an agreement.
An agreement is only possible if the ZOPAs of both parties intersect. If party A is willing to pay 100-1000$ but party B asks for 1000-2000$, even the best negotiation tactic in the world will be unsuccessful. Finding out your partner’s ZOPA in advance of the negotiation will give you an idea about the likelihood of a deal. During negotiation’s both parties keep introducing new demands – this will keep increasing the ZOPA.
The «0 ZOPA»-Phase
Zero ZOPA is another word for dead lock. Everything has been said, all facts have been analyzed, and there is no more room to manoeuvre. Breaking the deadlock is possible by introducing new demands or by breaking off and re-entering negotiations.