On a trip to China in 2009, I climbed to the top of a 13-story pagoda in the industrial hub of Changzhou, not far from Shanghai, and scanned the surroundings. Construction cranes stretched across the smoggy horizon, which looked yellow in the sun. My son Daniel, who was teaching English at a local university, told me, “Yellow is the color of development.”

During my time in Beijing as a Journal reporter covering China’s economy, starting in 2011, China became the world’s No. 1 trader, surpassing the U.S., and the world’s No....