The research found that Black taxpayers were three to five times more likely than taxpayers who are not Black to be audited. It noted that the I.R.S. disproportionately flagged tax returns with potential errors in the claiming of certain credits, like the earned-income tax credit, which supplements low-income workers’ incomes in an effort to alleviate poverty.

It sounds like it could be a side effect of disproportionately auditing lower-icome people, mixed with income inequality affecting black taxpayers.