Simon Bridges, leader of the party of the rich, is spreading the usual scare stories about how taxing capital income will see people leaving New Zealand. Its supposed to suggest that the tax will be ineffective, that people will leave the country to avoid it. Except that most of these assets - investment properties, farms, small businesses - are immobile. So whether they sell up when they move, or keep their assets and remain as foreign absentee landlords, it doesn't matter: the asset is still here and can still be taxed, regardless of who owns it or which foreign country they hide in. They simply can't take it with them when they go. Which is why Bridges and his rich masters are so upset by the idea: finally, they won't be able to hide, and will have to pay their fair share.
As for the idea that an exodus would be some sort of loss to New Zealand, I doubt it. Someone who flees the country to avoid paying their fair share is someone we were better off without. Let Australia have them - they'll fit right in with the corrupt arseholes over the Tasman.
But while a capital gains tax is a great idea, its not enough: we should be going further, and taxing the wealth of the ultrarich directly, as suggested in the US by Elizabeth Warren. The rich have leeched off our government and society for too long. Time to make them pay their way.