Mercantile Exchange Adds Shares to IPO

The Chicago Mercantile Exchange said Tuesday that it would expand a planned initial public stock offering to 4.75 million shares worth as much as $161.5 million by selling stock held by members.

Exchange members will offer 1.75 million shares for sale, in addition to the 3 million shares already planned for the offering, Chicago Mercantile Holdings Inc. said in a filing with the Securities and Exchange Commission.

The holding company, which operates the nation’s largest futures market, had said the stock would be priced between $31 and $34 a share. The 4.75 million shares would amount to 15% of the shares to be outstanding after the offering, the filing said.

The exchange hasn’t set a date for the offering.