Late last month, Mr. Zucman and Mr. Saez discussed their work from their university offices in Berkeley, with billion-dollar views of the San Francisco financial district in the background.

They acknowledged their critics and the uncertainties involved in their research, which attempts to assemble a picture of America’s wealth distribution that is essentially invisible in standard economic data. But they defended their methods and conclusions, and said they were not surprised that the wealth tax, which polling shows is popular even with a majority of Republicans, had captured the imagination of candidates and voters.

“Clearly it’s been central to the campaign,” Mr. Zucman said, citing voter dissatisfaction with the levels of inequality in America.

But he added: “Let me be very clear that the wealth tax is not going to solve all these problems. It’s part of the solution.”

Both Mr. Saez and Mr. Zucman have built their careers studying the rise of inequality and its intersections with tax policy. In 2009, Mr. Saez won the John Bates Clark Medal for leading what the American Economic Association called “a remarkable resurgence of interest in tax policy research over the last decade.”

Mr. Zucman began his doctoral studies in economics that year. The son of two doctors in Paris, he wrote his master’s thesis on the effects of France’s wealth tax on the migration of high earners and spent the fall of 2008 interning at a Parisian financial firm. Lehman Brothers, the investment bank, collapsed on his first day, and he found himself explaining the macroeconomic dynamics of a financial crisis to panicked traders. It helped inspire him to pursue a doctorate in economics.

Mr. Zucman eventually made his way to Berkeley, where he teamed up with Mr. Saez, who, along with another French economist, Thomas Piketty, was producing pioneering research that documented the rising share of income earned by the very richest Americans in recent decades. Mr. Saez and Mr. Zucman, building on that data, showed that wealth had grown more concentrated as well.