He also thinks Loan to Value (LVR) limits should be phased down.
Bolton was making these comments in an interview for GRTV.
DTIs are currently being worked on by the Reserve Bank, which wants them ready by next year in case they are needed to rein in any future upward rush of house prices.
They would join LVRs in the bank's toolkit of anti-inflation mechanisms.
The recent fall in house prices has taken some of the urgency out of the DTI programme, but Bolton still sees merit in them after earlier opposing them.
He says DTIs are a constant measure which ignores fluctuating interest rates and is therefore more suited to the fact that real estate purchases are a long term thing.
“I have been in my house for over 20 years.”
Bolton's view is that a DTI regime would smooth over the rise and fall of interest rates, and the consequent rise and fall of stress testing levels. They would also reflect more accurately people's ability to pay for a long term project like buying a house.
They could also avert the pain of dealing with a stress testing rate, which has reached 8.5% to 9% in response to actual mortgages reaching a 6.95% median for two-year fixed loans.
In his comments, Bolton also suggested that LVRs might be moving past their use-by date.
“They were appropriate when house prices were too high,” he said.
“But they have done their job and they did a good job, because otherwise we would have had a lot more buyers with negative equity positions.
“But because the banks have got a 10% speed limit, they are only approving main bank customers and they are not pre-approving, you have to have a house under contract, so the rules are limiting the ability of people to buy a home.”
Bolton said it would be appropriate to pull the LVR restrictions back from first home buyers, but they should perhaps be kept on for property investors.
