Bring it on, say budget hawks: such a stalemate would mean reverting to the level of the 2010 budget.

ECONOMIST: Much stroppiness lies ahead in the EU budget negotiations

But for the market as a whole, for which profit margins are beautifully mean reverting, it is exactly the reverse.

FORBES: Bubble Talk: Grantham Warns Of The Paradox Of Profit Margins

Profit margins, he says, are mean-reverting, meaning that at times when margins are high, investors should be willing to pay less per dollar of earnings.

FORBES: Bubble Talk: Grantham Warns Of The Paradox Of Profit Margins

For example, the presumption that economic life repeats itself, eventually reverting to the mean, makes statistical work easier.

ECONOMIST: Economics focus

Arnott tested the theory to see if this was simply a case of earnings reverting to the mean.

FORBES: The great stock illusion

In the next four-year segment they not only dropped out of the top funds but averaged annual gains of only 1.8%, reverting to the mean or worse.

FORBES: Swear Off Individual Stocks For Better Returns

It is the hope, myth, or dream that there are money managers out there who can outperform the market year after year, never giving back their superior results or reverting to the mean.

FORBES: Everyone Wants Kool Aid: Pruning the Money Management Tree (October 29, 2008)