Commodity prices reached an all time high last month, but the prices exporters are getting continue to be diminished by the high exchange rate.
The ANZ commodity price index surged 12.6% in April, an all-time high for the index and the largest monthly rise in the history of the series which uses 1986 as the starting point for the index.
ANZ economist Steve Edwards said the surge in dairy prices - which makes up 40% of the index - has underpinned the rise, and excluding that, the index would only have increased by 0.2%.
But commodity prices could drop after Thursday's fall in global dairy prices.
Mr Edwards said easing commodity prices in the shorter term would largely reflect the weighting of the dairy price component.
When international prices are converted into local currency there's been a strengthening in the value of the New Zealand dollar against all our major trading partners, measured by the Trade Weighted Index, which diminishes what is being returned to New Zealand farmers.
Even so dairy prices have been so strong that they are even rising in New Zealand dollars, as measured by the bank's New Zealand Dollar Commodity Price Index.
Mr Edwards said the increase in terms of New Zealand dollars was 10.2% last month, which is about 8% below the all-time peak in March 2011.