This Year’s IPO Billionaires See Wealth Eroded by Market Moves

The long-awaited return of IPO activity this year minted 21 new billionaires, but what came after many companies’ eye-popping debuts was often a different story.

Insiders whose stakes ballooned to at least $1 billion on the first trading day have since seen the value of those holdings plunge by an average of 23% in the following weeks or months, according to the Bloomberg Billionaires Index.

“Hype and momentum can only take you so far,’” said Steve Sosnick, chief strategist at Interactive Brokers. “We saw no shortage of stocks and other speculative assets, new and old, have momentum-driven spikes ...