It’s official. American president Donald Trump has launched a new era of trade wars, with the sweeping tariffs he has imposed on Canada, Mexico and China primed to come into effect today. There is serious tit-for-tat energy, here. With Canada vowing to retaliate by imposing tax on Florida Orange Juice, Tennessee whiskey, and Kentucky peanut butter.  But how do tariffs actually work? Who pays for them? And just how much can they raise consumers’ bills, and damage - or help - any of these countries’ economies?    Today, Senior Economics correspondent Shane Wright, and North American correspondent Michael Koziol, on whether this is, as one newspaper has dubbed it, “the dumbest trade war in history.”Subscribe to The Age & SMH: https://subscribe.smh.com.au/See omnystudio.com/listener for privacy information.