Coal prices are on course for their biggest annual fall in more than a decade, hurting producers of the fossil fuel but cutting raw-material costs for struggling steelmakers. The spot price of thermal coal, which is burned to generate electricity, has tumbled 39% to $52.35 a metric ton so far in 2019, according to S&P Global Platts. If prices don’t rebound before the end of the year, the decline would be the largest one-year drop since Platts started compiling the benchmark price in 2007. …