Not sure but here’s my guess. Sandicor includes out of SD County home but I pull them out when I run stats. ZIP might have them included. I also only look at attached and detached while they may include 2 to 4 unit properties and land.
Most significant is that in February, Sandicor pulled homes without sq ftage listed out of the stats function that I use to pull numbers. They said they skewed the calculation of price/sq ft. Personally, I think there are problems with both numbers (ZIP and Mine). I dont recommend looking at the numbers as absolutes but rather a way to look at direction and velocity in the market. As long as I keep the methodology consistent we should get that. Make sense?
