Coal prices have soared this summer, after new mining restrictions curbed production in China, the world’s biggest producer and consumer. According to The Wall Street Journal, benchmark prices for thermal coal in Asia, Europe and the U.S. have climbed by more than a third since April, while the price of coal used in steelmaking is up 20% from its 2016 nadir in May. The rally is a stark reversal for the coal market, which has been in a protracted slide for much of the past five years. Ample production and waning demand in developed countries have pummeled prices. But in April, China’s State Administration of Work Safety introduced new coal-production caps, limiting the number of working days for its coal miners to 276 a year from 330 previously.