(Bloomberg) -- The surprising resilience of the US economy this year is masking underlying weakness among low- and middle-income households, as higher-income Americans continue to drive growth.

This dichotomy between the haves and have-nots isn’t new, but the economic strain is now bleeding from the lowest earners to the middle class, creating an even starker divide that some economists say makes the economy more susceptible to a downturn.

Most Read from Bloomberg

• Trump’s 90,000-Square-Foot Ballroom Plan Puzzles the Experts

• Can Anyone Save Gary, Indiana?

• Boston’s South Station Gets a Towering Makeover

• NYC Gets 12-Minute Helicopter for Suburbanites Avoiding Gridlock

• In Vancouver, A Court Ruling on Indigenous Land Triggers Real Estate Angst

The richest 10% of households are fueling nearly half of total US spending, thanks to a stock market surge that has boosted wealth and in turn propelled economic output this year. Meanwhile, lower-income families are pulling back in the face of tight budgets, still-high living costs and a raft of corporate layoffs.

Executives at companies like Chipotle Mexican Grill Inc., Hilton Worldwide Holdings Inc. and Ethan Allen Interiors Inc. have cited the trend in recent earnings calls, and Federal Reserve Chair Jerome Powell said officials are carefully watching signs of a bifurcated economy after the central bank lowered interest rates last week.

“I feel like our economy today resembles a top-heavy Jenga tower,” said Peter Atwater, the economist who, in 2020, popularized the idea of a “K-shaped” economy, where the well off are on an upward track and the less fortunate experience further declines.

In the popular Jenga game, wooden blocks are stacked and then carefully removed by players until the tower becomes too fragile and collapses. The reference is apt as the stock market surges to fresh highs even as hiring stalls and layoffs creep up.

While the robust pace of growth has surprised economists, especially amid the Trump administration’s significant policy changes, the divergence in spending — with an increasingly smaller group of people holding up the economy — is fueling concern that the US is becoming susceptible to a more pronounced slowdown.

“It makes the economy highly vulnerable if anything goes off the rails for those high-income, high-net worth households,” said Mark Zandi, the chief economist for Moody’s Analytics.

A downturn in the stock market “would knock the wind out of these high income households — the last pillars of strength in the economy — and raise the risks of recession,” he added.