Carl Icahn’s settlement of a regulatory investigation caps a 15-month period that has seen the investor’s net worth plummet by $19 billion.

Shares of Icahn Enterprises LP fell 4.7% Monday after the billionaire and his investment firm agreed to pay $2 million to settle Securities and Exchange Commission allegations that he didn’t provide enough information about how he was borrowing against his stake in the company.

The SEC settlement comes on the heels of a May 2023 report by short-seller Hindenburg Research, accusing him of operating a “ponzi-like” structure at IEP, the publicly traded partnership where Icahn is chairman and controlling shareholder. The company’s stock tanked after the Hindenburg report, which laid out a case that it was significantly overvalued relative to its underlying holdings, and that the company’s dividends may not be sustainable.

Over more than a year of stepped-up scrutiny of his business, the activist investor’s wealth has plunged to $5.8 billion from $24.8 billion before the Hindenburg report was published, according to the Bloomberg Billionaires Index.

A representative for Icahn didn’t immediately provide a comment.

According to the SEC’s allegations, since 2018 the 88-year-old investor pledged a majority of IEP’s securities units as collateral, allowing him to secure billions of dollars’ worth of personal loans, but IEP failed to properly disclose these arrangements until 2022. The agency also determined that Icahn didn’t appropriately amend securities filings to detail his personal margin-loan agreements until at least July 2023.

Icahn and IEP neither admitted nor denied wrongdoing. They agreed to pay fines of $500,000 and $1.5 million, respectively, to settle the claims. They also agreed to cease and desist from future violations, the agency said.

Shares of IEP have fallen 68% since the Hindenburg report was published on May 2, 2023. The short-selling firm, founded by Nate Anderson, also alleged IEP paid out dividends in a way that would only be sustainable “to the extent that new money is willing to risk being the last one ‘holding the bag.’”

The investor’s margin loans, first outlined by the Hindenburg report, weren’t previously accounted for by Bloomberg’s wealth index. Icahn’s fortune fell by more than $10 billion after the short-seller leveled the accusations.

Icahn has long specialized as a corporate raider and activist investor, buying large stakes in companies and pushing management for changes. Now living South Florida, Icahn has continued to seek out corporate targets.

“If you’re going to be bothered by this, you shouldn’t be in this business,” Icahn said last year in an interview with Bloomberg News following the Hindenburg report.

This article was provided by Bloomberg News.