NZDMO was conservative about changing its rates and did not alter them every time the market went up or down, she said.
Jeal did not believe there would be a further drop soon.
The amount raised so far is a tiny fraction of the overall costs to the Government but there was never an expectation that it would play a major part in paying for the Government's costs, Jeal said. "There was no target amount."
"It is simply an opportunity for New Zealanders to contribute to funding that was specifically earmarked for Christchurch but still get a return on their investment."
So far investors have predominantly been those putting in less than $50,000 and more than $100,000.
The minimum investment is $1000.
Jeal said some of the money had been reinvested from the Government's other Kiwi Bonds which existed before the Earthquake Kiwi Bond.
Retail investment in government bonds had declined in the past few years.
Jeal said investors had flocked to the safety of government bonds when the finance companies collapsed but when the banks were covered under the guarantee they had moved to the higher bank deposit rates.