President-elect Donald Trump has threatened to hit Mexico, Canada and China with new tariffs as soon as he takes office.

In a post on social media, Trump promised to charge Mexico and Canada an additional 25 percent tariff on all products they send to the US - and an additional 10 percent tariff will be placed on Chinese goods.

Infometrics Principal Economist Brad Olsen says these trade changes come with ramifications for the rest of the world - New Zealand included.

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