The TSX Composite is plunging downward again Friday after a week of large and consistent losses related largely to falling commodity prices. The TSX has staggered badly out of the gate in 2018, falling nearly 1.6 percent to post the fourth-worst performance to start the year among 93 global exchanges. The Canadian benchmark index is slotted between Oman’s exchange and London’s FTSE 100. In the US, there is similar aversion among investors to improving employment and industrial strength. The Dow average was down more than 250 points by midday Friday.