Who knows which security the margin loss of $42m relates to?
https://investors.interactivebrokers.com/ir/main.php?file=latestEarningsPR As previously disclosed, over an extended period in 2018, a small number of our brokerage customers had
taken relatively large positions in a security listed on a major U.S. exchange. We extended margin loans
against the security at a conservatively high collateral requirement. In December 2018, within a very short
timeframe, this security lost a substantial amount of its value. The customer accounts were well margined
and at December 31, 2018 they had incurred losses but had not fallen into any deficits. During the current
quarter, subsequent price declines in the stock caused these accounts to fall into deficits, despite our efforts
to liquidate the customers’ positions. For the quarter ended March 31, 2019, we have recognized an
aggregate loss of approximately $42 million. The ultimate effect of this incident on our results will depend
upon market conditions and the outcome of the our debt collection efforts.