Merck, which always declines comment on merger rumors, was widely rumored to be interested in buying Sterling.

"So what do you think of all the buy-out and merger rumors we've been hearing lately?"

The authors were careful to filter out companies whose gain could be attributed to other causes, like a good earnings report or merger rumors.

The ruling could lead to the end of a routine practice by companies of saying "no comment" when asked about merger rumors that are, in fact, correct.

For months, the two companies have been the subject of merger rumors, although it is believed that talks became more serious in the past two weeks.

But at this year's show, there is also another theme: merger rumors.

And First Interstate, which merger rumors immediately named as a possible Wells Fargo target, leaped $6.125, to $33.875.

With many stocks already rising on merger rumors, analysts are scrutinizing hundreds more to identify tomorrow's targets.

The two companies, which have been the focus of merger rumors, said no agreement had been reached.

JWT stock had never gone above $41.50 until merger rumors agitated the stock market.