Americans worth more than $100 million sat on a whopping $8.5 trillion in untaxed profits in 2022, a report released Wednesday found — money that may never be taxed unless Congress closes a loophole shielding the investments of the ultrarich.

These centimillionaires and billionaires made up just 0.05% of all American households in 2022, according to Federal Reserve data analyzed by the progressive nonprofit Americans for Tax Fairness. But they held one-sixth of so-called unrealized capital gains in the country.

Unrealized gains are the primary source of income for many elite families. Under current law, growth in the value of assets like stocks, bonds, investments, real estate or businesses is not taxable until they are “realized,” or sold. The ultrawealthy can nonetheless live off these gains by taking out low-interest loans against their exorbitant wealth. And when their fortunes become inheritances, the gains are no longer taxable.

“The superrich truly live in a strange and privileged world,” said David Kass, the executive director of Americans for Tax Fairness. While most households depend on paychecks — “income that is taxed all year, every year,” Kass noted — these untaxed gains make up the largest single source of income for the ultrawealthy.

“The scandal of tax-free billionaires,” Kass added, also results in billions of dollars less in tax revenue that could fund health care, housing, education and other public programs.

Led by President Joe Biden, Sen. Ron Wyden (D-Ore.) and Reps. Steve Cohen (D-Tenn.) and Don Beyer (D-Va.) have introduced a “Billionaires Income Tax” in both chambers of Congress. The tax would apply only to unrealized gains held by ultrawealthy households, and could generate an estimated $500 billion in new revenue over a decade.

Biden has also proposed ending the loophole, known as the stepped-up basis, that erases capital gains for tax purposes when wealthy individuals pass on their fortunes as inheritance. Both plans have virtually no support among Republicans.

Without congressional action, the untouchable wealth of the superrich is likely to only grow. Since 1989, when the Federal Reserve began collecting this data, households worth more than $100 million have nearly tripled their share of the country’s unrealized gains.

The disparity in how the incomes of the superrich are taxed also deepens racial divides.

Of the $8.5 trillion in untaxed wealth belonging to centimillionaires and billionaires, $7.6 trillion, or almost 90%, is held by white households. That figure is six times the total wealth of all Black households in the country, and five times the total wealth of all Hispanic households.