Perth rents dropped further in December with the median price dropping by $10 to about $440 a week.
Real Estate Institute of Western Australia president David Airey said the shift was more noticeable in apartments and villas.
"Houses are typically holding a rental median of $450 per week while units, apartments and villas have dropped to a median of around $420 per week," he said.
Perth's vacancy rate has risen to 4.2 per cent, with about 6300 rental properties on the market. Mr Airey said a three per cent vacancy was normal, and the current high rate was largely due to slowing population growth in response to fewer jobs.
"The increase in stock over the past two years can be directly attributed to the rapid turnaround in migration which peaked in the year to September 2012," he said.
"The latest reading of WA's population growth for the year to June 2014 has it falling to its lowest level in eight years."
REIWA data showed the number of properties for lease rose by 10 per cent in the December quarter and was up by 37 per cent on a year ago. Areas with the strongest increases in rental listings last year were Belmont, Kwinana, Armadale and the northwest corridor of Wanneroo.
Kwinana was the only area to increase its median rent last year, up by $5 to $390 a week.
Armadale remains most affordable with a median rent of $370 a week.