The cost of complete core memory systems was dominated by the cost of stringing the wires through the cores. Forrester's coincident-current system required one of the wires to be run at 45 degrees to the cores, which proved difficult to wire by machine, so that core arrays had to be assembled under microscopes by workers with fine motor control. Initially, garment workers were used. By the late 1950s industrial plants were being set up in East Asia to build core. Inside, hundreds of workers strung cores for low pay.