Among financial stocks, Citigroup fell 2 11/16, to 65 1/8.

The researchers believe not, since they were unable to find a similar pattern among stocks for which no options exist.

It does not lead them to forget about distinctions among stocks.

Among small stocks, technology and gambling issues, which have ricocheted all over the board in recent weeks, were hard hit.

The market's recent losses have wiped out much of the year's earlier gains, especially among smaller stocks.

There are some distinctions among stocks from different countries.

Prices held up somewhat better among smaller stocks on the Amex.

Bargains are sometimes found among stocks of companies in merger negotiations, he said.

They found, for example, that the pattern is strongest among stocks held primarily by individual investors.

Among large-cap stocks, he said in a recent interview, "our effect on the market is more one of noise."