"We do believe we are getting close to a top and perhaps the major banks passing on the bank levy might just be the point which creates a trigger for a slowdown. We will wait and see."

Mr Christopher also said a downturn could be closer after observing a rise in unreported auctions in 2017 against the bumper level of 2015.

Last weekend about 25 per cent of auctions were unreported, while in 2015 – when the Sydney market was rising at its fastest rate in 30 years – about 18 per cent were unreported. That said, volumes of auctions were also about 10 per cent lower in 2015, making it easier for data to be collected.

"In life, there is a tendency to want to report good news but not so much the bad news," he said.

When auction clearance rates fall to around 65 per cent in Sydney, a housing downturn is official, property analyst SQM Research managing director Louis Christopher says. Jim Rice

"As such, when there is a rise in unreported rates it may suggest there is increasing bad news in the property market, notwithstanding any surge in listings which may make it difficult for auction reporting teams to compile the results before the day is out."

Higher listings, while welcomed by real estate agents who need stock to meet demand, also suggested vendors might be pre-empting the market to be close to peak, Mr Christopher added.

Corelogic said, ahead of its May house price results due on Thursday morning, that negative movements in house prices were to be expected.


Early figures released by CoreLogic on Tuesday ahead of that data, showed that Sydney values were down 1.3 per cent and Melbourne values fell 1.8 per cent in the first 29 days of May.

"The weak preliminary result is largely influenced by a month-on-month fall in Sydney and Melbourne dwelling values, however, when seasonal factors are taken into account, the May result isn't likely to be as weak as the headline results are indicating," CoreLogic head of research Tim Lawless said.

"Importantly, the trend rate of growth shows the pace of capital gains has moderated from recent highs; this slowdown is occurring against a backdrop of rising mortgage rates, softer auction results, rising advertised stock levels, lower housing market sentiment and slowing investment activity."

These need to be considered against a traditionally low auction season for May and the winter months.