Tax Day Highlights Inequality, Experts Call for Wealth Tax

Mayor Mamdani, Nobel laureate Stiglitz, and economist Zucman warn that extreme inequality is "fundamentally unsustainable" and urge taxing the ultra-rich.

Apr. 16, 2026 at 12:56am

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A minimalist illustration using primary-colored geometric shapes and clean lines to conceptually represent the need for a wealth tax to address extreme inequality.A bold visual statement on Tax Day calling for a fairer tax system to address extreme wealth inequality.NYC Today

In a new opinion piece, Mayor Zohran Kwame Mamdani, Nobel laureate in economics Joseph Stiglitz, and economics professor Gabriel Zucman warn that today's levels of inequality are "fundamentally unsustainable" and driven by the failure to effectively tax extreme wealth. They highlight efforts in New York to introduce a pied-à-terre tax targeting the second homes of the ultra-wealthy to help fund essential public services.

Why it matters

Extreme inequality has reshaped daily life in New York and around the world, undermining social and political cohesion, eroding trust in institutions, and leading people to conclude that the system is rigged. Allowing a system where extreme wealth exists alongside widespread hardship, where the ultra-rich can opt out of contributing to the society that enabled their success, is fundamentally unsustainable.

The details

The authors note that in the 1960s, the 400 richest Americans paid about 50% of their income in taxes, but today they pay only about 24%. This pattern of the super-rich paying lower effective tax rates than almost everyone else is not unique to the US, but seen across Europe and in countries like Brazil as well. They argue that the ultra-wealthy's wealth depends heavily on public investment, yet the burden is shifted onto working people whose taxes sustain the very systems that enable extreme wealth.

  • Tax Day is on April 15, 2026.
  • In 2024, the G20 put the issue of effectively taxing the ultra-wealthy on its agenda and commissioned a report proposing a minimum 2% wealth tax on the super-rich.
  • In 2025, Spain and Brazil committed to leading a coalition of countries to implement the G20's wealth tax proposal.
  • This weekend, the Spanish Prime Minister and Brazilian President will meet with other world leaders in Barcelona to press ahead with the wealth tax initiative.
  • In the US, California voters will consider a tax on billionaire wealth this November, and Washington state has approved a 9.9% income tax on million-dollar incomes starting in 2028.

The players

Zohran Kwame Mamdani

The mayor of New York City.

Joseph Stiglitz

A Nobel laureate in economics and university professor at Columbia University.

Gabriel Zucman

A professor of economics at the Paris School of Economics and École normale supérieure - PSL, and the Director of the International Tax Observatory.

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What they’re saying

“The idea that billionaires should pay higher tax rates than working people is not radical. What is radical is allowing a system where extreme wealth exists alongside widespread hardship - and where those billionaires can in effect opt out of contributing to the society that made their success possible.”

— Zohran Kwame Mamdani, Joseph Stiglitz, Gabriel Zucman, Mayor of New York City, Nobel laureate in economics, professor of economics

What’s next

The Spanish Prime Minister and Brazilian President will meet with other world leaders in Barcelona this weekend to press ahead with the G20's wealth tax proposal. In the US, California voters will consider a tax on billionaire wealth this November, and Washington state has approved a 9.9% income tax on million-dollar incomes starting in 2028.

The takeaway

Extreme inequality has become a global crisis, with the richest 1% capturing 41% of all new wealth between 2000 and 2024 while the bottom half of humanity got just 1%. Effectively taxing the ultra-wealthy is essential to restoring economic balance, rebuilding trust in institutions, and ensuring everyone can live with dignity.