** South Korean refiners tumble as falling oil prices darken
their profit outlook
** Shares of S-Oil 010950.KS fall as much as 6.6 pct,
while those of GS Holdings 078930.KS and SK Innovation
096770.KS decline 6.3 pct and 6.4 pct, respectively
** Oil markets drop by around 1 percent in 2019's first
trading on Wednesday, pulled down by surging U.S. output and
concerns about an economic slowdown in 2019 urn:newsml:reuters.com:*:nL3N1Z204L
** U.S. crude futures end 2018 down 24.8 pct from end-2017,
while brent crude futures end 2018 down 19.5 pct from end-2017
** The broader KOSPI market .KS11 trading down 1.7 pct as
of 0554 GMT
((hayoung.choi.thomsonreuters.com@reuters.net))