Before one stock traded on Wall Street on Jan. 22, the world had telegraphed its view of the slumping U.S. economy.

The Hong Kong market followed up Monday's 5.49 percent dive with a 7.22 percent decline on Tuesday. The Nikkei in Tokyo slumped to a low point not seen since September 2005. Mumbai's Sensex Index plunge of 7.4 percent on Monday was the second-worst ever. And the Frankfurt Stock Exchange nosedive was its worst since Sept. 11, 2001.

Then the Federal Reserve slashed interest rates with an unheard of "emergency U.S. rate cut." It wasn't enough: The Dow Jones Industrial Average took an early-morning nosedive. President Bush continued to talk up an "economic stimulus plan." And the weak U.S. dollar fell sharply against the Euro.

All was not well.

Certainly few could pinpoint blame on IT departments for causing all the turmoil or count on IT chiefs for quick fixes to the credit crunch, subprime mortgage crises, housing slowdown and jobless rate climb.

But the recent turn of events and sour forecasts for 2008 raise intriguing questions of exactly what IT's role is at publicly traded companies, how much a CIO and his IT operations can influence Wall Street, and what CIOs should do to keep their companies in the good graces of its shareholders.

CEOs and CFOs can all talk a pretty good game about how mission-critical IT systems are these days, but just how much does IT actually matter to those who work on Wall Street?

The answer, it turns out, is both simple and difficult. The simple version is that IT matters a lot when systems and networks go horribly and publicly wrong, as these things sometimes do. The bigger-picture view is that IT run very well can make internal operations more efficient for bottom-line results.

But the fight to get credit for that work on Wall Street is like the mechanic who gets little credit for a well-cared-for and dependable car, say CIOs and financial analysts. A car should run along smoothly, shouldn't cost too much to maintain and should take good care of its passengers. Surprises ought to be rare.

"If everything is going swimmingly with a company and its stock, then IT doesn’t matter [to Wall Street]," says Patricia Edwards, a portfolio manager and managing director at Wentworth, Hauser and Violich who focuses on retail. But if systems are ignored and IT investment is continually chopped, then, to borrow the car maintenance analogy, "companies won't notice it at 7,000 or 8,000 miles, but they will notice it at 15,000 miles," Edwards says. "Sometimes it doesn’t matter until it matters." Like when the muffler falls off when you're heading down the interstate at 75 mph.