Concern over the possible return from exile of deposed ruler Ferdinand Marcos triggered a four-day slide on Philippine stock exchanges that continued Thursday with two major markets losing nearly 10 percent this week. President Corazon Aquino, questioned about the drop, repeated her resolve to abide by any decision of a court considering Marcos' petition to return to defend himself at a hearing concerning an alleged $5 million kickback scheme. "I stand by my commitment respecting the decision of our courts," said Aquino who two days earlier vowed to personally ensure the safety of Marcos if he returns from his Hawaiian exile for the hearing. That remark set off a sharp retreat on the markets.