A stronger dollar amplified last month's fall - the sixth in a row - in export commodity prices.
ANZ's commodity price index fell 0.5 per cent in July in world price terms, to be 20 per cent off its peak in April last year and back where it was in March 2010.
On average last month the exchange rate was 2.2 per cent higher on a trade-weighted basis than in June, so in New Zealand dollar terms ANZ's index fell 3.1 per cent, to be 26 per cent off its peak last year.
ANZ economist Mark Smith said the price decline had broadly tracked the fall in global prices given uncertainty over the European debt crisis.
Of the 17 commodities in the index, prices fell for 10 and rose for just three, with four steady.