But such projections always depend on the economy evolving in line with its expectations. "The balance of developments over the past few weeks has pointed in the direction of less inflation pressure," he said.
On a trade-weighted basis the kiwi dollar has traded between 2 and 3 per cent higher than the Reserve Bank assumed, at the same time as dairy prices have dropped sharply - by 20 per cent since early February.
"If export prices had gone up instead of down and the exchange rate was higher the Reserve Bank would say the shock here is that export prices have gone up, and the exchange rate has just responded to that and taken a lot of the inflation pressure out," Stephens said.
"But that is not what has happened here. There is a completely separate exchange rate shock and it must require a lower forecast for the future OCR - fewer OCR hikes."
But probably only one fewer over the next two years, a cumulative 1.75 instead of 2 percentage points, Stephens said.
ASB chief economist Nick Tuffley said the New Zealand dollar had not been performing its buffer function of falling to offset weaker export prices.
"It is entirely possible and appropriate that the New Zealand dollar does fall and catch up to this particular fundamental," he said.
But the Reserve Bank also faced the uncomfortable reality that it was going it alone among the developed world in lifting interest rates, and that made New Zealand stand out for global investors, resulting in a risk that the dollar is stronger for longer.
"That risk may start to colour the bank's OCR decisions beyond April," Tuffley said.