- Muddling through (most likely): Greece seeks to stay in the euro but doesn’t agree to unconditionally implement the reform program. The most likely consequence is that the Troika ceases payments, though banks continue to receive European Central Bank support unless a political decision is made to withdraw central bank facilities. Greek membership in the euro depends on its ability to adjust to new incentives as the threat of exclusion from the rest of the bloc gains credibility.

-- Slow exit (next-most likely): Greece is excluded from the euro area after the remaining members are given time to build firewalls against the shock, such as deposit guarantees and liquidity injections by the ECB. While there isn’t a legal mechanism for exclusion, it could be done in practice by cutting Greek banks off from ECB facilities and payments systems. For the rest of the euro area, the firewalls are unlikely to be robust enough to deal with the impact of the Greek exit, while there may be market fallout because of the new precedent that euro membership can be rescinded, Goldman says.

-- Fast exit (least likely): Greece abandons the euro and introduces a new currency. A “sudden and abrupt” exit wouldn’t give other nations time to prepare and an insufficient firewall could mean an unraveling of the euro area.