EquiLend is owned by banks including the six other defendants, according to its website. Equilend didn't immediately comment. In stock-lending transactions, firms lend out their shares to borrowers for a fee, often using agents as middlemen. There are some $1.72 trillion of shares on loan at any one time, the suit says. Private lawsuits have already drawn billions of dollars in settlements over the alleged manipulation by banks of foreign-exchange, interest-rate, commodity and off-exchange derivatives markets. Twelve banks and two industry groups in 2015 agreed to pay $1.87 billion to settle accusations that they rigged the credit derivatives markets. In 2013, Iowa's pension fund was the lead plaintiff in a class-action lawsuit against Countrywide Financial Corp. and others over alleged abuses in the packaging and selling of mortgage bonds that soured in the financial crisis. Defendants agreed to pay $500 million to settle that case.