The country's purchasing power against other nations is continuing to drop.
Official figures show the terms of trade fell 3.2% in the three months to September from the previous quarter, the biggest drop this year.
The drop means fewer imports can be bought for every dollar of exports sold.
Export prices fell 6.3% led by a 13% drop in dairy prices, while import prices fell 3.3% after a 13% drop in petrol prices.
ANZ New Zealand senior economist Mark Smith says the strength of the New Zealand dollar continues to affect the export market.
Infometrics economist Benje Patterson says the index should stabilise into next year as dairy export prices recover.
Dairy exports rise by a third
Dairy export volumes rose by 32% in the September quarter, the official figures show, with milk powder the largest contributor to the rise.
Dairy products made the largest contribution to a 9.7% rise in seasonally adjusted export volumes.
Meat exports rose by 15%.