China’s fixed-asset investment grew at its slowest rate in nearly 15 years in May, missing expectations even as growth in retail sales and factory output steadied, arguing for Beijing to increase policy support to avert a deeper downturn. Fixed-asset investment, a crucial driver of the world’s second-largest economy, rose 11.4 percent in the first five months of this year from the year-earlier period, missing a Reuters poll forecast for a 12 percent gain, the same as in April.