Millions of consumers visit Zillow every month.
It is a computer-generated estimate of the value of a home today, given the available data.
 These recalculations are based on a variety of considerations and, therefore, not every new algorithm release will get a corresponding update of historical values.
The algorithms determine the approximate added value that an additional bedroom or bathroom contributes, though the amount of the change depends on many factors, including local market trends, location and other home facts.