FORTUNE — There are economic losers and winners after any natural disaster. This week, restaurants, movie theaters, airlines, and department stores will lose billions as Hurricane Sandy leaves millions without power and access to transportation.
Home Depot (hd), on the other hand, is likely to see a bumper quarter, providing generators and heavy-duty flashlights to many of the estimated 60 million people hit by the storm.
But whether the economy as a whole wins or loses is up for debate. Some analysts are arguing that Sandy could act as a kind of grisly stimulus package, mostly thanks to the billions of dollars that will be spent repairing flood and wind damage. The idea isn’t totally out there: unemployment in post-Katrina New Orleans actually fell in the aftermath of the storm. And some academics say that reconstruction after storms in well-prepared areas can boost the economy.
But storms in general, and this one in particular, rarely deliver the kind of stimulus Keynesians are hoping for this week.
One-off catastrophes tend to have a negligible long-term effect on the larger economy, positive or negative, even when there is a tragic human cost. In the aftermath of Hurricane Katrina, while regional unemployment dipped, national GDP growth slowed, if only slightly, says Erwann Michel-Kerjan, co-director of the Wharton Risk Management and Decision Processes Center. Sandy, orders of magnitude smaller, will hardly register on the national radar.
Regionally, there’s reason to be bearish on Sandy. Conservative estimates of the storm’s cost from risk management firm Eqecat range from $10 billion (about what 2011’s Hurricane Irene cost) to $20 billion (closer to what Hurricane Ike in 2008 cost). Michel-Kerjan says that some 60% of those costs will likely come from lost business. That’s a reversal from past natural disasters, where some 40% of the cost has typically come from lost businesses, with the rest coming from damaged property. Sandy is different, Michel-Kerjan says, because it has shut down several major population centers for an extended period of time and, unlike Hurricane Irene, it hit during the workweek.
The result? Billions in lost revenue. And unlike the bills for repairing property damage, which benefit other parts of the economy, much of the lost business revenue will never be recouped. Take Starbucks (SBUX), which closed its New York stores during the storm. “You’re not going to go out and buy twice as much coffee on Wednesday [when the storm lets up],” says Evan Gold, a senior vice president at weather consulting firm Planalytics.
Some of the costs will be transferred to other businesses. For example, Outback Steakhouse’s loss could be Kroger’s (kr) gain. But that’s a zero-sum game for the economy, or worse, if consumers don’t spend as much on the meal. “People are shifting and changing, but in many cases they lose out on an opportunity to do something,” Gold says. That’s especially meaningful just before the holiday season. Says Gold: “Macy’s is not going to get days like this back. It’s November. Every day counts.”
Along with Macy’s (M), apparel companies like Gap (gps) and J. Crew are also in for a hit. Others losers include jewelry retailers, casual restaurants, and entertainment destinations, like movie theaters, casinos and theme parks, according to Planalytics. For just about all major retailers, at least 10% of their locations will be affected by the storm. For some, it’s higher. BJ’s has 54% of its stores in Sandy’s path, Macy’s has 25%, Sears (shld) has 19%, and Target (tgt) has 16%.
Not everyone is a post-Sandy business loser, though. Wal-Mart (wmt), Target, and Safe Way (SWY) will likely get a bump. Drugstores could also get a boost, as people stock up on prescriptions, along with quick-service restaurants like McDonald’s (mcd), particularly those locations along evacuation routes.
Some individual products will see an uptick. Planalytics predicts that consumer demand for bagged ice in Boston will rise 133% between Oct. 27 and November 1. Demand for dehumidifiers in New York could rise 111%. And demand for rain gear in Cleveland is projected to increase by 91%. On Amazon (amzn), the sales rank of solar-powered and hand-cranked smartphone chargers soared over the weekend.
Gold says that grocery stores are often not affected by storms, despite the must-talked-about runs on bottled water. Lost foot traffic and reduced sales afterward usually cancel out the initial gains.
With flood levels reaching four or five feet in some cities, the total property damage bills are likely to be vast. Eqecat predicts that insurance will cover about half of the total cost of the storm (though that figure is less of a boon for a region that’s also home to the bulk of the country’s insurance companies). Government aid, too, will provide some lift to battered homeowners and businesses. In recent history, public officials have occasionally taken a no-holds-barred approach to reviving growth, providing low-interest loans and credit for post-disaster home repair. But there are a few reasons that may not be the case this time.
Howard Kunreuther, another co-director at Wharton’s risk management center, has studied government assistance to affected areas post-crisis, and says that, this year, policymakers may feel pressure to keep payouts low in light of mounting government debt. Another wildcard: Kunreuther’s research shows that disasters before an election draw more government relief than disasters after an election. He notes that, at the moment, politicians are vowing to rush to the region’s aid. Kunreuther is doubtful, though, that Congress will be able to make a move before the Nov. 6 elections.
Still, there may yet be a silver lining for the economy. The storm could prompt an increase in spending on weather-ready buildings and infrastructure in preparation for future disasters. Those types of investments could lift the economy more than post-crisis repairs — and are more likely to actually save lives. “Spending before the disaster is really where you have the best return on investment,” says Wharton’s Michel-Kerjan. The challenge is generating enthusiasm in the absence of a calamity. “No one wants to go to Wal-Mart if there’s not a hurricane on the news,” he said.
Michel-Kerjan projects the costs to sufficiently storm-proof the entire United States would be in the trillions of dollars. By comparison, the potential costs and profits from a storm like Sandy look like a rounding error. Stimulus, indeed.