South Korea’s trade boom quieted in October after export growth of 7% missed economists’ expectations of a 16% pickup. The slowdown from the prior months’ 35% growth was the result of a 13% drop in automotive exports (from a 60% growth) while steel grew by just 5% from a more-than-doubling. Exports to the U.S. fell 12%, the fastest rate of decline since July 2016. That may reflect a temporary effect from last year’s recovery from Hanjin Shipping’s failure in September. The trade surplus with the U.S. narrowed, and at $18.4 billion in the past 12 months is well below its $25.9 billion pea...