Inflation in January likely rose 0.4% from December, while core inflation, which excludes volatile food and energy items, may also be up 0.4%, according to a Reuters survey of economists last week. Rising gasoline costs and sticky prices throughout the economy are partly responsible for inflation’s staying power in the U.S., and will likely reinforce the Federal Reserve’s view that the fight against rising prices is far from over.

A hot inflation report this week could leave markets jittery about whether the Fed will stay the course with smaller interest rate hikes or go for more aggressive action to cool the economy. But Tuesday’s numbers may not be telling the whole story about inflation, according to Nobel Prize–winning economist Paul Krugman.

In a tweet Sunday, Krugman forecasted “a significant uptick” in inflation, but added that Tuesday’s report likely will lack enough data to accurately predict inflation’s future path. While the report will likely show prices have risen, Krugman wrote, it will be “for reasons that tell us little about how we’re actually doing on inflation.”

Where inflation goes from here

Predicting inflation’s trajectory is a risky game that has tripped up many economists over the past few years. Krugman himself has admitted making mistakes in 2021, when he and other economists forecasted inflation to be a fleeting factor in the U.S. economy that would wane soon enough.

But while some economists warned that soaring inflation last year would require a severe recession and a sharp rise in unemployment to fix, Krugman remained optimistic about the Fed’s chances of engineering a soft landing and averting a deep recession, predictions that have so far been validated by the economy’s relative health this year.

The road to taming inflation is a long one, however, despite recent positive news, and bumps along it are almost inevitable. “The disinflationary process, the process of getting inflation down, has begun,” Fed Chair Jerome Powell said last week, but added: “It has a long way to go. These are the very early stages.”

Inflation’s expected rise this month will come down to prices for some items rising after months of declines, which may have been temporary. Krugman pointed to a recent reversal in used car prices, which rose 2.5% between December and January after falling 15% in 2022. Gasoline prices have also risen around 4% since last month, ending months of declines since prices peaked last year when the Ukraine War scrambled energy markets.

What all this points to is that temporary factors that kept inflation down for the past few months are fading, Krugman wrote, leading to an uptick in prices. But this doesn’t necessarily mean inflation is set to soar to another 40-year high as it did last summer.

Shelter costs for one, which the Bureau of Labor Statistics uses to measure housing prices, may be deceivingly high on paper. U.S. housing costs have fallen significantly in the past few months after soaring in 2021 and early 2022, but the official shelter costs that factor into inflation calculations are expected to stay high for the next few months, as housing price measurements tend to lag behind actual market costs.

In anticipation of this week’s report, analysts have said that while inflation is set for an uptick it does not mean the fight against rising prices has been lost. While shelter prices and a tight labor market will continue applying upward pressure to inflation, “underneath the surface, many of the cyclical subcomponents driving CPI appear to be headed in the right direction,” Jason Pride, chief investment officer of private wealth at Glenmede, told Fortune.

A recent adjustment to how often the BLS weighs price changes in different years may also lead to a higher-than-expected inflation reading this week, but it doesn’t mean the Fed’s plan to reduce inflation has been tainted.

“Core inflation should move higher again in January as core goods deflation takes a pause and methodological changes boost the housing component,” analysts at Morgan Stanley wrote in a note last week. “Updated index weights could inject additional volatility, but we see the path to disinflation intact beyond January.”

An uptick in prices last month would show that the path to bringing inflation to manageable levels is a long and uneven one, but by and large things are still going to plan, the Morgan Stanley analysts wrote.

“My baseline view is that the economy is still probably running unsustainably hot, and that inflation is down substantially but probably running above target,” Krugman wrote.