April 15, 2026
FOR IMMEDIATE RELEASE
NEW YORK – 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 in large part by the failure to tax extreme wealth.
Writing for The Guardian, the authors highlight how extreme inequality has reshaped daily life in New York and around the world and why taxing the ultra‑rich is essential to restoring economic balance and democratic trust.
“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.
The longer we wait to fix that, the more entrenched wealth and economic and political power become, further cementing the privileges of our modern aristocracy.”
The piece also underscores efforts underway in New York, where advocacy by the Mamdani administration has led to the introduction of the first-ever pied‑à‑terre tax targeting the second homes of ultra‑wealthy property owners to help close the city’s budget deficit and fund essential public services.
In case you missed it, read the full piece in The Guardian below:
The Guardian
Tax day is a reminder of America’s unequal tax system. But we can fix it
April 15, 2026
Today, we have more income and wealth inequality than ever before. New York City’s average household income is $131,000. Without extreme inequality, residents could live reasonably well. Instead, a few people at the top of the income ladder capture enormous wealth, while millions of others struggle just to get by. Some simply can’t make it. For them, New York has become fundamentally unaffordable.
This outsized level of inequality has enormous economic, political and social consequences. It undermines social and political cohesion, erodes trust in institutions and leads people to conclude, correctly, that the system is rigged.
Nearly one-fifth of America’s super-rich live in New York, the highest concentration of wealth in any state. But inequality is not just a New York problem or even an American problem – though the United States is more unequal than almost every other advanced economy. It is a global crisis.
The global inequality report, commissioned during South Africa’s G20 presidency, found that between 2000 and 2024, the richest 1% captured 41% of all new wealth, while the bottom half of humanity got just 1%. This trajectory is unsustainable.
The rise of extreme wealth is one of the clearest signs of this imbalance. In 1987, billionaires held wealth equal to 3% of global GDP. Today this tiny elite, just 0.0001% of the world population, owns the equivalent of 16% of world GDP in wealth.
As wealth concentrates, so does power – the power to influence elections, shape policy, tilt markets and define the terms of public debate.
One of the main drivers of this trend is our collective failure to effectively tax the super-rich. Until recently, the scale of the problem was difficult to measure. Public data does not track tax contributions of the ultra-wealthy. But recently, there has been a flurry of research looking at just that, and the findings are clear.
In the 1960s, the 400 richest Americans paid about 50% of their income in taxes across all levels of government. Today, they pay about 24%.
This is not unique to the US. Across Europe – including France, Italy and the Netherlands – and in countries such as Brazil, researchers find the same pattern: the super-rich pay lower effective tax rates than almost everyone else. They excel not only at making money, but at avoiding and evading taxes.
Even when they do pay, it falls far short of their fair share – despite the fact that their wealth depends heavily on public investment: government contracts, a highly educated workforce, a rule of law that facilitates business or good infrastructure, or even the basic technology that underlies their “innovation”. Instead, the burden is shifted on to working people whose taxes sustain the very systems that enable extreme wealth.
It is high time we confront this problem collectively.
We can disagree about how progressive tax systems should be – the extent to which the rich should pay more tax, relative to their income, than the rest of us. But there is no justification for a regressive system in which the super-rich contribute less than the rest of us. This is how inequality is deepened and sustained.
For too long, reform has been dismissed as too complex or politically infeasible, even as voters across the political spectrum enthusiastically support the rich paying what they owe.
That is beginning to change.
In 2024, under Brazil’s leadership, the G20 put this issue on its agenda and committed to more effective taxation of ultra-high-net-worth individuals. It commissioned a report that proposed a minimum tax of 2% on the wealth of the super-rich – a straightforward way to ensure they meet their obligations to society.
That powerful idea has had ripple effects. In 2025, Spain and Brazil committed to leading a coalition of countries to implement it. This weekend, the Spanish prime minister, Pedro Sánchez, and Brazilian president, Luiz Inácio Lula Silva, will meet in Barcelona with the heads of states of South Africa, Mexico, Colombia and many more countries to press ahead.
In France, a version of this minimum tax passed the National Assembly, though it was blocked by the conservative Senate. Still, it remains central to the national debate – much like the income tax itself, which once faced similar resistance from conservative forces before becoming law. In the US, a paradigm shift is under way. California voters will consider a tax on billionaire wealth this November. Washington state has approved a 9.9% income tax on million-dollar incomes, set to take effect in 2028. In New York, we are calling on the state to increase taxes on the rich and large corporations to close New York City’s budget deficit and fund essential public services like affordable housing and childcare. And we are already making progress with a new pied-a-terre tax in New York City, which will tax the ultra-wealthy and global elites.
These are just the first steps toward restoring a basic social principle: that those with the most should contribute their fair share so that everyone can live with dignity.
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.
The longer we wait to fix that, the more entrenched wealth and economic and political power become, further cementing the privileges of our modern aristocracy.
Joseph E Stiglitz is a Nobel laureate in economics, university professor at Columbia University and chief economist of the Roosevelt Institute
Zohran Mamdani is the mayor of New York City
Gabriel Zucman is professor of economics at the Paris School of Economics and École normale supérieure – PSL and Director of International Tax Observatory