This is a key housing market to follow since Phoenix saw a large bubble / bust followed by strong investor buying.

The Arizona Regional Multiple Listing Service (ARMLS) reports (table below):

1) Overall sales in August were up 0.4% year-over-year.

2) Active inventory is now down 7.4% year-over-year. 

More inventory (a theme in most of 2014) - and less investor buying - suggested price increases would slow sharply in 2014.  And prices increases did slow in 2014, only increasing 2.4% according to Case-Shiller.

In 2015, with falling inventory, prices increased a little faster.  Prices were up 6.3% in 2015 according to Case-Shiller.

With flat inventory in 2016, prices were up 4.8%.

This is the tenth consecutive month with a YoY decrease in inventory, and prices are rising a little faster this year (2.8% through June or 5.7% annual rate).

August Residential Sales and Inventory, Greater Phoenix Area, ARMLS
  SalesYoY
Change
Sales
Cash
Sales
Percent
Cash
Active
Inventory
YoY
Change
Inventory
Aug-085,660---1,00417.7%53,5691---
Aug-098,00841.5%2,84935.6%38,085-28.9%
Aug-107,358-8.1%3,12942.5%44,30716.3%
Aug-118,71218.4%3,95345.4%26,983-39.1%
Aug-127,574-13.1%3,38244.7%20,934-22.4%
Aug-137,055-6.9%2,40934.1%21,4442.4%
Aug-146,431-8.8%1,62125.2%26,13821.9%
Aug-157,0239.2%1,58822.6%22,554-13.7%
Aug-167,97513.6%1,61620.3%23,3183.4%
Aug-178,0100.4%1,54119.2%21,590-7.4%
1 August 2008 probably includes pending listings