well actually between the closing of COX and now, about 1 year their stock are actually over all, went up. When COX closed, it was at about 156,000 won a share (Nov 16 2012 closing). Right now it's about 215,000 won a share.
It dipped down in the first few days of Dec 2012 to about 147,000 won a share, then went back up to closed at 165,000 Dec 14 2012. It hit it's lowest within the past year Feb 6 2012 at 128,000 and been over all climbing up since then.
5 year trend
Nov. 20 2008, it's stock closed at 39,000won. Nov 18th 2013 closed at 215,500. (keep in mind it's about Tuesday 4 am odd 19 Nov. 2013 in Seoul, Korea.)
So overall, their stocks haven't been going down since the closing. Their stocks actually started dropping overall in 2011 about oct 24 2011 from 369,000 won a share to 299,000 by nov 25 2011 and down ever since until recently starting uptick overall after going down to 128,000 in feb 2013. Basically the down turn of their stock prices started before the announcement and while COX was well and alive. The down turn is not because of the closing of COX, although it may or may have not have helped. Overall whether COX was alive or dead seemed to have miniscule effect on the stock prices unless it could also be said that it caused their down turn too way back in 2011 COX did indeed have a major effect and and they are now recovering from the damage. But more than likely, the case is that COX didn't have hardly any type of effect and the closing didn't have much effect either. Because even their lowest since COX closed is above their lowest when COX was alive and way prior to the announcement.
If someone recently purchased a substantial amount of stock, in feb 7th, now they would have made a decent sized profit for such a short amount of time.