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Don't fall for Wall St. if there's good news from Greece

COMMENTARY Reports of a possible deal on Greek debt have Wall Street primed for another one of those mayfly rallies that now take place on any whiff of possible good economic news. Don't fall for it. Mayflies' life cycles last -- at most -- a couple of days, and any rally will be shorter than that.

If Greece and its creditors can come to terms (and that is a huge if) it will mean that a huge shock to the world financial system has been postponed, again. The two sides are haggling over exactly how little creditors will get back on their investments. These negotiations have about as much relation to reality as arguing over the number of angels who do the hula on the top of a pin. Greece can pay zero -- nothing -- on its debt. It cannot pay 100 percent, it cannot pay 20 percent or anything else. Greece is so bankrupt that even if its debts were entirely forgiven, it would still be totally bankrupt. That is the key fact to remember anytime you read anything about this.

These negotiations are not about repaying anything. They are about coming up with a way not to have to call this a default. If that happens, then hedge funds start calling in credit default insurance, and the world's financial system will get that deer-after-it's-been-run-over-by-an-18-wheeler look. This prospect is so scary that it may even get those hedge funds to think twice about forcing a situation where they can collect on their insurance.

So what does this all mean to you and me? Keep your powder dry and your money out of the markets. Even if Greece by some miracle comes to terms with its creditors, there are still the economies of Spain, Ireland, Italy and Portugal to contend with before Europe is out of the woods and we can all breathe a bit easier.

Watch the volume of the markets, not whether the Dow or anything else is up or down. When a lot of people return to the markets for more than a day or even a week, then you'll know it's safe.