China's official purchasing managers' index fell more than expected to 50.4 in May, the weakest reading this year and down from April's 13-month high, in the latest sign that output in the world's second-biggest economy is cooling.Economists polled by Reuters had expected the official PMI, which captures activity in the biggest factories in the country - many of them state-backed - to retreat to 52.2 for May, from 53.3 in April.Small...