Now, unfortunately, because it is an election year, we are apparently going to have the debate that we have every single election year: should we set up a special unit that costs each party's election promises independently?

And the answer to that question should be the same as it always is - no, we should not do this.

There is no point in doing it. This unit will not be independent. It will be stacked with the same people who stack the public service - predominantly left-leaning public servants who will overestimate what a capital gains tax will bring in because they like a capital gains tax and who will underestimate the benefits of cutting red tape because they are the red tape.

To believe this unit's numbers, you would first have to believe Treasury’s numbers because it is probably people from Treasury who will go and work in a unit like this.

If you believe Treasury, here’s a word of advice: go outside at midday with a stick and a string and see what the spirits tell you is going to happen in the future - because that is about how useful Treasury’s numbers are.

If you want to know what a biased referee looks like in an election year, this is it: an 'independent' costings unit.

If we were to set this thing up, all we would end up doing is the same thing we already do with Treasury numbers - arguing all the time about whether they’re right or wrong.

Actually, you and I are pretty good arbiters of whether costings add up. We all spotted immediately that Labour’s $65 million for the public transport policy was not enough money. 

We didn’t need an independent unit to tell us that - we looked at it and thought, 'That’s not enough money, mate, you’re going to have to do those numbers again.'

We all knew last election - we talked about it for months - that National had completely overestimated how much money it would get from a foreign buyers’ tax. And were we right? Yes, we were.

We don’t need another unit that costs more money, adds more bureaucracy and is stacked with more bureaucrats and we don’t need another unit to tell us what we can already figure out ourselves.

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