Power is being rationed in Shanghai because of shortages created by insufficient coal supplies and a seasonal drought, which has reduced the generation of hydroelectric power. Shopping centers and department stores must turn off their heat between 10 a.m. and noon, and small factories have been shut down. China’s power supply hasn’t kept pace with the booming economy, and deeper rationing may be necessary. Shanghai’s population is now estimated to be more than 20 million, up some 3 million in the last year alone.