"IF WE EXPECT LARGE CHANGES but are very uncertain as to what precise form these changes will take, then our confidence will be weak." So wrote John Maynard Keynes in his classic General Theory of Employment Interest and Money in 1936. That might explain why consumer confidence fell 14 percent after Katrina cut a swathe through Louisiana, Alabama, and Mississippi, to its lowest level since 1992.

Like markets, consumers abhor uncertainty. And uncertainty abounds. Weather forecasters are now joined by economic forecasters as the stars of 24-hour business new channels. As the economists dance to the weather forecasters' tune, and revise and re-revise their own forecasts, oil and natural gas prices dance to the economists' tune.

Meanwhile, sober analysts attempt to look beyond these short-term blips, but do little to reduce uncertainty. Well-regarded authorities say we are exhausting crude oil supplies so rapidly that we are on a route to $200-per-barrel, while equally well-credentialed experts expect renewed exploration activity to drive prices below $40.

When the storms abate, the uncertainties do not. The president has said he will spend whatever it takes to restore New Orleans to what some like to remember as its pre-hurricane glory, forgetting that the city was losing jobs and commercial tenants long before the floods came. "Whatever it takes" has already come to over $60 billion, and is likely to exceed $200 billion by the time returnees are rehoused and the president's new war on poverty has been waged.

What forecasters are trying to figure out is how this effort will be financed. If the government simply adds to the deficit, inflation might be triggered by this further loosening of fiscal policy. If, instead, the Democrats prevail and raise taxes, with businesses and high earners the likely targets, economic growth might be slowed. If the politicians decide to postpone the start of the massive prescription drug program, the health care and pharmaceutical industries will feel the pain. And if the relief effort is financed by cutting the road-and bridge-building program, the construction industries will be hurt. No hope for certainty soon.

Then we have heightened uncertainty about the future course of interest rates. Some Fed watchers say the central bank's decision last week to continue raising interest rates is the beginning of the end of that process. Others say that the fact that the price of gold has reached an 18-year high foretells a round of inflation that will force the Fed to continue raising rates. Still others say it is impossible to predict monetary policy when the 18-year rein of Alan Greenspan comes to an end in January. Anyone caring to guess at the future path of interest rates would to well to keep in mind what Keynes called "the extreme precariousness of the basis of knowledge on which [such] estimates" are based.

These uncertainties are magnified by the meaninglessness of the economic data recently made available. Most information was compiled before Katrina struck, wiping out upwards of 100,000 jobs, driving gasoline prices above the $3-per-gallon level, and shaking confidence in the government. It is a reasonable guess that the recovery effort will provide jobs for displaced workers, or that they will find work in the regions to which they have migrated. After all, the Texas economy, to which many New Orleans residents have been moved, creates about 12,000 jobs per month, and the national economy around 200,000.