One of the most surprising recent moments in U.S.-China relations arrived last September in Washington D.C. when Barack Obama and Chinese President Xi Jinping told reporters they’d reached a deal to end state-supported hacking of corporate records for economic benefit.

Why would China agree to give up an activity that appeared to have been a crucial part of its economic strategy? Based on recent observations of Chinese hacking activity and the country’s recent economic plans, analysts at U.S.-based cybersecurity firm FireEye...