Who decides on house prices and their fluctuation?

Question

On the news it might say "house prices have fallen 2.7% in the last month" for example but who decides that house prices have fallen 2.7%, how did they come to that amount and why?

Answer 1

Actually the home buyer decides what homes are selling for.

Ever heard " It's a Buyers market"homes prices are down.

"Its a Sellers market " home prices are up...

To get the percentage (2.7% ) they compare last month to (?) last years prices for example..Its the difference of what homes are selling for now ,compared to what these homes  have sold for in the past