Didi Kuaidi was forged last year by the merger of rival taxi-hailing apps controlled by Alibaba and Tencent, two Chinese internet giants. It now dominates China’s online market for personal transport. Last year it arranged 1.4 billion rides in China, more than Uber has done worldwide in its history. It has perhaps two-thirds of the market for private-car rides (the source of most of its revenues) and provides a taxi-hailing service in several hundred cities. Uber, with a third of the market for private-car service, this week announced plans to expand to cover 55 Chinese cities. Both have spent heavily on subsidies to lure drivers to sign up.