The last week has been even worse for grocery chain J Sainsbury ( LSE: SBRY ), whose share price has fallen 9% in that time. Half-year trading figures showed underlying retail operating profit down 7.2% to £308m, like-for-like sales off 1% and underlying earnings per share sliding 6.7%. On the plus side, online and convenience store sales did increase. The group is o n track to deliver £500m of cost savings by 2017/18, with another £500m savings target to follow. It also cut net debt by £485m to £1.3bn, giving it one of the strongest supermarket balance sheets.