China’s quantitative funds have built trading strategies so closely tailored to the mainland market that foreign rivals cannot replicate them, even as a regulatory clampdown on trading speed reshapes the industry, according to a prominent economist. “If a top US quant team goes to Japan or India, they can beat virtually all the native quants,” Xia Chun, founder and chief economist at Chinese financial research firm Wiselink Group and former finance professor at the University of Hong Kong, told...