Bitcoin's meteoric rise has weighed on South Korea's small-cap stocks. It has surged nearly 35 percent since Mr. Trump won the election on Nov. 5, while the small-cap Costco index has fallen 8 percent, making it likely to be Asia's worst performer this year. Analysts say the decline is partly due to small investors selling stocks for bitcoin, adding to the rout that has wiped about a fifth of the index's value this year. Trading volume on South Korean cryptocurrency exchanges has now exceeded th...