WELLINGTON, Sept 28 (Reuters) - The Reserve Bank of New Zealand (RBNZ) said on Monday it has made a surplus of NZ$624 million ($398 million) in the 2014-15 financial year, the second largest in the bank's history, thanks to large gains made in the foreign exchange market.
A 13 percent decline in the trade-weighted index (TWI) =NZD in the year ending in June resulted in a NZ$379 million gain for the bank, it said, in sharp contrast to last year's NZ$198 million loss.
The central bank intervened in the foreign exchange market in 2014 by selling the then strong New Zealand dollar which was described as 'unjustified' and 'unsustainable" by Governor Graeme Wheeler.
The New Zealand dollar NZD=D4 has shed 25 cents since it hit a post-float peak in mid-2014. It was last at $0.6372, not far from six-year lows touched last month.
Much of the weakness is due to a sharp fall in the prices of dairy products, the nation's top export earner, and a slowdown in its prime export market, China. The RBNZ cut rates to 2.75 percent earlier this month and flagged more easing.
The RBNZ also said it would pay a NZ$510 million dividend to the government, the second largest ever. ($1 = 1.5689 New Zealand dollars)