Stock markets worldwide keep swinging as President Donald Trump's trade war keeps escalating. The S&P 500 was bobbing between small gains and losses in early trading Wednesday. The index is about 19 per cent below its record set less than two months ago.

The Dow Jones Industrial Average was down 170 points, or 0.5 per cent, and the Nasdaq composite was 0.5 per cent higher. Overseas markets were sharply lower. The swings came after Trump's latest round of tariffs kicked in after midnight, imposing taxes on imports from around the world, and China retaliated with more tariffs of its own. Treasury yields rose sharply.