Kiwibank has dominated mortgage lending by registered banks since the December quarter of 2008 and, although its hectic growth has slowed in recent quarters, continues to lend at a much greater rate than its market share.
"Kiwibank is getting them (mortgages) because they've made the decision they want that business," Tripe says. In Kiwibank's absence, the mortgages it has been writing would have been shared around the other banks, making little difference to the overall amount of mortgages written, he says.
Excluding SBS Bank, which became a registered bank in October 2008, mortgage lending by registered banks rose $0.97 billion in the December 2008 quarter and Kiwibank accounted for a staggering 89.7% of that.
In the nine months ended June 2009, Kiwibank accounted for 45.9%, or $2.27 billion, of the $4.95 billion in mortgages written by registered banks. Over the following year, it accounted for 29.4% of the $6.34 billion written.
In September 2008, Kiwibank accounted for 3.76% of the bank mortgage market. By June 30 this year, it accounted for 6.11%.
"I don't think it (Kiwibank's existence) has made any difference as to whether the business has been done in the first place - maybe a little bit of difference at the margin," Tripe says.
Similarly, if the proposed "heartland bank," formed from the merger between Pyne Gould's Marac and the Canterbury and Southern Cross building societies, gains the banking licence it hopes for, it's unlikely to make a huge difference to how competitive the banking market is, Tripe says.
"They're simply going to be too small in any market segment - they will provide competition around the edges," Tripe says.
"Heartland bank" had total assets of $2.2 billion at June 30 compared with SBS Bank's $2.58 billion and its mortgage book was just $278.5 million.