Ms. Warren, from Massachusetts, is not the only Democratic presidential candidate to promise to corral the galloping growth of riches controlled by those at the top. But she has steered away from demonizing it like Senator Bernie Sanders of Vermont, describing herself as a “capitalist to my bones.”

In a post on Medium, she said she was simply asking “those who have done really well in the last few decades to pay their fair share.”

And she detailed her plan in response to rival candidates who demanded that she explain how she would pay for her “Medicare for All” proposal, rather than in response to complaints that her previous ideas did not sufficiently soak the superrich.

But if her methods and motivation differ, the result would be similar. Over time, billionaires would have many fewer billions.

Gabriel Zucman, who has advised Ms. Warren, said that is the point. “You had a good idea at 30, that’s great, you can be a multibillionaire for 10 to 20 years,” he said of entrepreneurs in an email. “What an annual wealth tax of 6 percent does is that it makes it harder to stay a multibillionaire at age 70, 90, etc. It makes wealth circulate.”

He and Emmanuel Saez, both economists at the University of California, Berkeley, estimated what the impact would have been if Ms. Warren’s wealth tax had been in effect from 1982 to 2018.

The combined trove owned by the 400 wealthiest Americans would be 42 percent of the $2.9 trillion total that Forbes estimated last year.