But it’s not just an abstract concern—it’s already happening.

Martin Ott, the CEO of Taxfix, the Berlin-based tax app valued at more than $1 billion, exclusively told Fortune some of its wealthy U.K.-based clients have been eyeing an exit—but he doesn’t recommend it. 

“Yes, there are certain customers, at a certain income bracket, that are moving to save money abroad,” Ott, a former Meta exec, said. “I always encourage people to stay where you are.”

‘You have a social responsibility to invest in your country’ 

In 2025, more millionaires have left the U.K. than in any other nation. According to the Henley Private Wealth Migration Report 2025, about 16,500 millionaires uprooted last year, totaling about $91.8 billion. This translates to a 9% reduction in the U.K.’s millionaire population over the last decade, in part thanks to fallout from Brexit, political uncertainty, and tax changes. 

But Ott argues that leaving now is shortsighted. If the country’s top founders and high earners leave, it will weaken the very ecosystem they once thrived in. 

“Saving taxes is one thing, but at the same time, you also have a social responsibility to make sure you invest in a country,” he explained.

In his eyes, wealth creates an obligation to keep the ecosystem healthy for the next wave of builders, operators, and job seekers. Ott says that’s why many of his friends and peers—people who could easily decamp to Dubai or Montenegro—are deliberately staying put. 

“They’re saying, we’re not moving…We really want to make sure we also give back and build cool stuff that makes it worthwhile staying.”

To him, the more responsible choice is to weather the cycle, build through it, and strengthen the system from inside: “You don’t want a brain drain…I can only just encourage everyone to stay, build great new businesses, create an environment where entrepreneurs want to start something.”

Plus, pressure creates diamonds

Looking back on his early fintech days in London during the financial crisis, Ott recalled holding hundreds of millions of customers’ money in bank accounts, not knowing if the banks would survive the next day—and he said it taught him a lesson that still matters now.

“There was also that feeling that the world is going down. Do we need to move somewhere else? No, everything goes in phases,” Ott said. He credits the dark period with teaching him “what it means to go through crisis,” including how to manage his own personal health and how to be a better manager to others when the chips are down. But more importantly, it highlighted that downturns aren’t forever.

“Taking a more balanced, long-term view—that’s what I learned,” he added. “Things aren’t as bad as they look in the moment.

“And then new opportunities are born, and you can deal with crisis, because it’s constant, you’ll always have stuff that’s getting thrown your way.”

A version of this story originally published on Fortune.com on November 25, 2025.

Read more on wealth from Fortune’s Orianna Rosa Royle:

Berkshire Hathaway (BRKA +2.82%) (BRKB +2.80%) has held American Express (AXP +0.34%) for nearly 40 years, making it a staple holding under former CEO Warren Buffett. I predict Berkshire will continue to hold American Express under Warren Buffett’s hand-picked successor, Greg Abel, because the company is attracting new cardholders from younger generations through its highly appealing rewards program.

Here’s why the value stock is a great buy now.

American Express is winning with millennials and Gen Zers

In the second quarter of 2026, as American Express reported on July 24, Gen Xers accounted for 36% of spending volumes among individual consumers, followed by 31% from millennials, 27% from baby boomers and older, and 7% from Gen Zers.

However, Gen Zers showed 40% year-over-year spending growth, followed by 14% from millennials, 10% from Gen Xers, and 5% from baby boomers. Although Gen Xers and baby boomers account for the majority of consumer spending, the fastest-growing cohorts are younger generations.

Today’s Change

(0.34%) $1.13

Current Price

$336.52

Key Data Points

Market Cap

$227BMarket cap calculated using publicly traded shares outstanding only. Does not include unlisted, private, or dual-class non-traded shares. Implied market cap may vary.

Day’s Range

$331.85 – $336.81

52wk Range

$288.34 – $387.49

Volume

116.6K

Avg Vol

3.2M

Gross Margin

59.74%

Dividend Yield

1.05%

American Express’s secret sauce

Cross-generational engagement is the holy grail of consumer brands. It’s how fellow Berkshire core holding Coca-Cola became a beverage enjoyed across age groups and geographies, and how Apple built an ecosystem that incentivizes families to adopt the next generation of Apple products.

To achieve cross-generational adoption, a brand has to offer something above and beyond the competition. And for American Express, that’s a rewards program unlike any other. For the six months ended June 30, American Express raked in $5.61 billion in net card fees but spent a staggering $9.94 billion on card member rewards.

So even though its annual Gold Card membership now costs $325 and the Platinum Card costs $895, members are still getting a good deal based on the value of their rewards.

The beauty of American Express’s business is that it can afford these ultra-generous card member perks because its main revenue stream is what’s known as discount revenue, which is the fees it collects from merchants each time an American Express card is swiped, inserted, tapped, or entered digitally. For the six months ended June 30, American Express generated $19.68 billion in discount revenue.

Anchor your portfolio with a high-quality stock

American Express has built an ecosystem that can endure for generations to come. It starts with a network of 155.1 million cards in force, which creates network effects that incentivize merchants to accept American Express even though the cards tend to have higher fees than Visa and Mastercard.

In turn, American Express generates substantial discount revenue, which it can use to offer generous perks to card members that cost nearly twice what members pay in annual fees. Because members are getting such a good deal, they are incentivized to rack up as many reward points as possible, which boosts discount revenue from merchant fees — and the cycle repeats.

American Express is attracting new card members and guiding for double-digit revenue growth and record earnings in 2026, even though consumer spending has been under pressure. The results and forecast show that the business can thrive regardless of the economic cycle.

Add it all up, and American Express stands out as arguably the single best Berkshire Hathaway stock to buy now.