Known as the Patriotic Millionaires, the group—which includes celebrity Mark Ruffalo and heiress Abigail Disney—called for a solution to end extreme wealth in a petition endorsed by PMUK, Tax Me Now, and Millionaires for Humanity. “You, our global representatives, have to tax us, the ultra rich, and you have to start now,” they said in a letter addressed to the leaders attending the Davos forum. 

It’s an echo of a similar open letter they sent to Davos attendees last spring. Citing the growing wealth inequality over the past 50 years, they noted that the world’s 10 richest men saw their wealth double during the pandemic, while 99% of the population watched their incomes shrink as they struggled to afford today’s cost of living. Indeed, a growing number of billionaires have been making out like kings over past few years.

Billionaires’ wealth has increased daily by about $2.7 billion ever since 2020, according to research from international poverty nonprofit Oxfam in conjunction with the Patriotic Millionaires. Meanwhile, poverty increased for the first time in half a century. Oxfam said imposing a 5% tax on multimillionaires and billionaires could raise $1.7 trillion annually, helping 2 billion people escape poverty.

Taxing the ultra-rich is “simple, common-sense economics,” the Patriotic Millionaires write in their letter. “It is an investment in our common good and a better future that we all deserve, and as millionaires we want to make that investment.”

They said that wealth inequality is tied to other dangerous extremes such as nationalism and climate change. They called upon those at Davos to address the “root cause of division,” adding that defending democracy is tied to creating a fairer economy.

“Extreme wealth is eating our world alive,” said Abigail Disney in a press release. “It is undermining our democracies, destabilizing our economies, and destroying our climate. But for all their talk about solving the world’s problems, the attendees of Davos refuse to discuss the only thing that can make a real impact—taxing the rich.”

The World Economic Forum did not immediately respond to Fortune’s request for comment. Disney has been a longtime critic of the systems that support the ultrarich, most recently blasting those who used private jets instead of opting to fly business class.  

But a growing group of billionaires is slowly promising to give away their fortunes. When asked by CNN if he planned to give away most of his wealth during his life, Jeff Bezos said, “Yeah, I do.” He recently endowed a $100 million gift to Dolly Parton to give to a charity of choice. Mackenzie Scott, Bezos’ ex-wife, has donated $12 billion in two short years.

Warren Buffett also plans to give away 99% of his wealth within 10 years of his death, possibly to every child across the globe. Along with Bill Gates and Melinda French Gates, he created the Giving Pledge, a campaign that some of the world’s richest people have signed as a promise to donate the majority of their fortunes to philanthropic causes.

Last year, Gates tweeted that he will one day “give virtually all my wealth” to the Bill & Melinda Gates Foundation. In a recent Reddit Ask Me Anything, Gates referred to chipping away at his wealth as a “full-time job.” While he said he wouldn’t ban any billionaires, he said he was “surprised” taxes hadn’t been increased.

But these promises of eventual charity aren’t fast and binding enough to address real-time wealth inequality, at least if you ask the Patriotic Millionaires.