I lost all faith in Zillow when I realized their estimate was just a number based on their guess at a price per square foot times the square footage...
A properties historical "Zestimate" changes if you update the current square footage. Whatajoke!
I somehow doubt it's that simplistic, though I imagine price/sqft is a heavy factor. And it should be, really. If you can find sales in the neighborhood and compute their price/sqft, there should be some relationship, modifiable by other features (pool, central air, etc.)
Case in point, my house's Zestimate comes out to $105/sqft, and my neighbor's comes in at $100/sqft. A neighbor without a pool's house comes in at $96/sqft. That would indicate that their "guess" is where the magic is - a price per square foot is computed based on factors that are not readily apparent.
It's most certainly not that simple. Valuation models have been around a long time and none are that simple. Perhaps it considers updates to be corrections to incorrect data. In which case recalculating the history seems reasonable to me
A properties historical "Zestimate" changes if you update the current square footage. Whatajoke!