Zillow Observed Rent Index
A monthly index of typical asking rent, published by Zillow for metro areas, counties and ZIP codes from repeat observations of the same rental units rather than a simple average of what happens to be listed.
The Zillow Observed Rent Index is "a smoothed measure of the typical observed market rate rent across a given region," built as "a repeat-rent index that is weighted to the rental housing stock to ensure representativeness across the entire market, not just those homes currently listed for-rent" (Methodology: Zillow Observed Rent Index (ZORI)).
The repeat-rent design compares the same units to themselves over time rather than averaging whatever happens to be advertised in a given month, which keeps a run of unusually cheap or expensive listings from moving the index on its own. Weighting to the rental stock, rather than to current listings, is meant to keep the index representative of what a place's rental market generally looks like, not only its most visible corner.
Zillow publishes the index in two forms: a seasonally adjusted series, used here for the level and every change reading, and a smoothed but not seasonally adjusted series, used here only to compare the current month against the typical month at this time of year. Reading a trend off the wrong series would either introduce a spurious seasonal sawtooth or erase the very seasonal signal the comparison is meant to show, so the two are never substituted for each other.
Coverage#
Monthly values from January 2015 through the most recent release, at three geographies: metropolitan and micropolitan areas, counties, and ZIP codes.
Rent history is much shorter than Zillow's home-value history, and coverage thins quickly the further back a comparison reaches. A one-year change is available in most of the places Zillow prices; a five-year change is available in a much smaller, differently distributed set of places, concentrated in larger and denser markets. For that reason a comparison against a ten-year horizon is not published for this index at any geography.
Geography#
The files are published for whole metro areas, counties and ZIP codes and are used at those grains directly. Census tracts are the exception, because Zillow publishes nothing at tract level: a tract's rent is assembled from the ZIP codes that overlap it, each weighted by the housing units the two share.
Where the overlapping ZIP codes have no published rent, the tract is left blank rather than filled in from the surrounding county — a missing ZIP code price is not a neutral gap, and a county figure standing in for it would be a confident guess about the places least suited to it. ZIP codes are handled as ZIP Code Tabulation Areas, the census geography built from the ZIP codes of the addresses inside it, close to but not identical with the postal ZIP code of the same digits.
Other considerations#
The index is nominal and is not adjusted for inflation. The seasonally adjusted series is already smoothed, so a single month's reading is not an independent observation of that month.
Metrics built on this source#
Citation#
Data Provided by Zillow Group
Zillow's terms permit non-personal use of the aggregate data, including derivative works, provided the Zillow Companies are credited on every page displaying the data, no Zillow logo is shown, and no relationship or endorsement is implied (Zillow Group Terms of Use). Figures derived from this index are our own; Zillow is not responsible for our calculations.
References#
- 1Zillow Research Datahttps://www.zillow.com/research/data/
- 2Methodology: Zillow Observed Rent Index (ZORI)https://www.zillow.com/research/methodology-zori-repeat-rent-27092/
- 3Zillow Group Terms of Usehttps://www.zillowgroup.com/developers/api/public-data/real-estate-metrics/