Consumer confidence is waning—and it's hurting retailers big and small. It has even come for the world's largest retailer, Walmart, which lost nearly $22 billion off its valuation on Tuesday.

Walmart's share price dropped about 3% by market close on Tuesday, resulting in its market cap falling to roughly $680 billion. This comes at the heels of mega e-commerce retailer Amazon dethroning Walmart in its quarterly revenue for the first time ever last month.

Uncertainty about the economy can be partly to blame. Consumer confidence hit a 12-year low amid concerns about tariffs and inflation, the Conference Board reported Tuesday. This was the fourth consecutive month consumer confidence fell. The index fell to 65.2, which is "well below the threshold of 80 that usually signals a recession ahead."

"Consumers' optimism about future income—which had held up quite strongly in the past few months—largely vanished, suggesting worries about the economy and labor market have started to spread into consumers' assessments of their personal situations," Stephanie Guichard, senior economist at the Conference Board, said in a statement.

Walmart CEO Doug McMillon had also warned about consumer confidence during a Feb. 27 talk at the Economic Club of Chicago. He noted that "budget-pressured" customers were reducing their spending and showing "stressed behaviors."

"You can see that the money runs out before the month is gone, you can see that people are buying smaller pack sizes at the end of the month," McMillon said.

Walmart declined Fortune's request for comment.

How consumer confidence affects companies' bottom line

Dwindling consumer confidence "is a worrying sign that our economic recovery may be stalling," WalletHub analyst Chip Lupo said in a statement to Fortune.

Other consumer-behavior experts warn that consumer confidence likely won't recover quickly.

"While the pain of inflation is hurting many Americans right now, the effect of inflation on your cost of living just compounds over time," Kelly LaVigne, vice president of consumer insights at insurance company Allianz Life, told Fortune in a statement. "That means inflation will continue to erode your purchasing power, unless you have a long-term strategy to address it."