One key factor is the number of skilled migrants to New Zealand passing up the regions in favour of the city.
"It's down to supply and demand," said Mr Nagel.
"Net migration is at its peak, but people are either stopping in Auckland, or catching the plane to Christchurch.
"This hampers growth in the smaller places - regional New Zealand isn't getting those new entrants."
A positive driver affecting the property market are Wellington commuters buying in Wairarapa.
But, said Mr Nagel, despite the numbers of these buyers growing by the day, "there are not enough to have an impact on the property boom".
New territorial authority rates taking into account the new property values will be effective from July 1, 2015.
While changing property values can affect rates, Masterton District Council spokesman Sam Rossiter-Stead says it is unlikely an increased housing value will mean greater rates in Wairarapa.
"The rating valuations are only one of the tools used to allocate rates between all properties," he said.
Mr Nagel says QV's value ratings will be audited by the Office of the Valuer General before home owners are informed.
He said Wairarapa home owners will receive their updated rating in late November.
Despite the drop in demand and market values, business has been "healthy" for Wairarapa estate agencies.
Property Brokers Wairarapa general manager Guy Mordaunt said business had picked up for vendors and buyers in the last month.
There had been a lull during the winter months, he said, mainly due to smaller numbers of first home buyers able to produce a 20 per cent deposit.
"The 20 per cent deposit really freaked them out - but more people are talking to their banks to find ways around it."
Mr Mordaunt said the flat values hadn't had a great impact on sales in the last year.
"A well-priced, well-marketed house will still sell."
Prue Hamill, of Harcourts-Hamill Realty, said a steady number of out-of-towners were buying in Masterton, attracted by its schooling, recreational facilities, cafes and community activities.
"People are slowly coming up this way," she said. "It's important for us in real estate to believe in the area, and sell it."