Insurance companies saw anomalous trading activities as well. Citigroup Inc., which has estimated that its Travelers Insurance unit may pay $500 million in claims from the World Trade Center attack, had about 45 times the normal volume during three trading days before the attack for options that profit, if the stock falls below $40. Citigroup shares fell $1.25 in late trading to $38.09. Morgan Stanley, which occupied 22 floors at the World Trade Center, experienced bigger-than-normal pre-attack trading of options that profited when stock prices fell. Other companies directly affected by the tragedy had similar jumps.