My post yesterday about the Budget concentrated on what I thought were some of the key higher level issues. But perforce you can't cover everything, and I didn't spend any time on whether Treasury's economic forecasts looked plausible or not.
Reading the various Budget commentaries that have come out since, however, apparently it's an issue that bothers some folk. So in an effort to clear the air, here's a table that compares Treasury's main forecasts (finalised on April 13) with the latest set of consensus forecasts collated by the New Zealand Institute of Economic Research (published on March 14). I've made them a bit more comparable by using Treasury's March year forecasts, rather than the headline June year forecasts in the Budget, and which are available on p138 of the Budget Economic and Fiscal Update: this matches the March years used in the consensus forecasts. There are still differences between them (eg some March quarter compared with full March year numbers), but they make no real difference. The Treasury set go out a year further than the consensus does.
My conclusion? They're not identical twins, but they're clearly describing the same economy. Treasury's got a slightly stronger GDP track, and when you unpack it and look at the more volatile components of GDP (house construction and exports), you find it's down to Treasury expecting a bigger and longer burst of housebuilding than the consensus did, and they could well be right.
There may well be a timing element involved, too. The set of consensus forecasts was collated after a very rocky period for global markets in January and the first half of February, when people had been anxious over the prospects for global economic activity (and particularly over China), and this may have helped produce a slightly weaker GDP outlook compared with Treasury's set, which had the benefit of seeing markets recover confidence in March.
But these are marginal points around the edges. For all practical purposes the Treasury forecasts aren't meaningfully different from the consensus. There's the odd item I'd quibble with - I wouldn't be surprised, for example, if Treasury's expected drop-off in net migration didn't materialise to the extent they think it will - but overall there's not a lot of evidence that Treasury's forecasts are idiosyncratically off the mark or systematically biassed.
And if you've still got some "smoke and mirrors" conspiracy view of the Budget numbers and projected surpluses, as I mentioned yesterday the overall picture of the fiscal position gradually moving into growing surplus comes through even when you use the alternative, lower growth scenario that Treasury also modelled in the Budget documents.