Provided by Dow Jones By Xavier Fontdegloria Business activity in the U.S. private sector continued to grow at an unprecedented pace in May but cost pressures kept mounting amid widespread supply problems. The flash reading for the U.S. Composite Output Index was 68.1 in May, up from 63.5 in April, preliminary data from IHS Markit showed Friday. The reading surpassed April's previous series record high, IHS Markit said. The indicator is based on data from the firm's PMI surveys for manufacturing and services sectors. For May, growth was driven by the fastest service sector upturn on record, with the increase in manufacturing output also accelerating amid stronger client demand.