Market Cap Drops by $400 Billion in a Day: What Happened to the Parent Company of the U.S. New Exchange?

Miami International Holdings Inc. (MIAX), a U.S. exchange operator, plunged 8.5% on the New York Stock Exchange, closing at $40.35. Trading volume increased to about 2.1 million shares, and its market capitalization fell to roughly $3.8 billion—about KRW 5.3 trillion—erasing around $300 million (approximately KRW 400 billion) in a single day.

In its first-quarter 2026 earnings report released in early May, the company posted net income and revenue growth that surpassed market expectations, driven by strong options trading, gains from the sale of a subsidiary, and tax benefits. This was followed by two major developments: the Options Clearing Corporation began clearing Bloomberg index futures products on MIAX Futures, a MIAX subsidiary, and on May 2, Chief Information Officer Douglas Shaeffer liquidated approximately $2.05 million worth of his MIAX shares.

Based in Princeton, New Jersey, and Miami, Florida, Miami International Holdings is the parent company of several U.S. electronic exchanges, including the MIAX, MIAX Pearl, and MIAX Emerald options markets; the MIAX Pearl Equities stock exchange; and MIAX Futures. Since launching its first options exchange in 2012 and listing on the NYSE in 2025, the relatively young public company has been regarded as a growth stock, rapidly expanding its market share in both derivatives and equity trading.