A widening probe of the foreign-exchange market is roiling anindustry already under pressure to reduce costs as computer platforms displace human traders.

Electronic dealing, which accounted for 66 percent of allcurrency transactions in 2013 and 20 percent in 2001, will increaseto 76 percent within five years, according to Aite Group LLC, aBoston-based consulting firm that reviewed Bank for InternationalSettlements data. About 81 percent of spot trading—the buying andselling of currency for immediate delivery—will be electronic by2018, Aite said.

“Foreign-exchange traders are much like stock floor traders: arapidly dying breed,” said Charles Geisst, author of “Wall Street:A History” and a finance professor at Manhattan College inRiverdale, New York. “Once the banks realize they are costing themmoney, the positions will dwindle quickly.”