Summary: Estimated monthly median market rent based on the Zillow Rent Index (ZRI) for all rental units. Values are for April 30th of each year and are not adjusted for inflation.
Data Source(s): Zillow Group, Inc., Zillow Rent Index (ZRI) for all rental units; U.S. Census Bureau, 2011, 2012, 2013, 2014, 2015, 2016, and 2017 American Community Survey 5-year Summary Files.
Universe: All rental housing units (multifamily, single-family residence and condo/co-op).
Methods: An extract of the monthly ZRI for all rental units (multifamily, single-family residence and condo/co-op) at the 2010 census tract level of geography was obtained from Zillow Group, Inc. The ZRI is "a smoothed measure of the median estimated market rate rent across a given region and housing type." Median "market" rent reflects the median rent of units up for rent at a given point in time, and not necessarily the median rent of all renter-occupied units. In places where rents are on the rise, median market rent will be higher the median rent paid by all renters and vice-versa. The underlying data used to derive the ZRI are the particular set of housing units for rent in a geographic area over at a given point in time. Because this sample of rental units may not reflect the overall rental housing stock in terms of types of units for rent, which could bias the estimate of median market rent, the methodology behind the ZRI is designed to adjust for differences between the sample of units for rent and the overall rental stock to yeild an index of median market rent that is unnaffected by the mix of homes in each sample used. For example, imagine a neighborhood that is mostly comprised of multifamily apartments, but for some reason most of the units up for rent at a given point in time are single-family units. Since single-family units tend to be more expensive, this could bias the estimate of median market rent upward if no adjustments were are made. A "smoothed measure" simply means that the ZRI for any given month is a three-month average to smooth the volitility in the estimates that can occur from one month to the next. ZRI estimates for April 30 of each year from 2011 through 2017 were selected for all census tracts in the 9-county Bay Area, and merged with data on the number of renter-occupied housing units from the 2011 through 2017 American Communty Survey (ACS) 5-year summary files (i.e. eight different 5-year summary files). ZRI values were estimated for geographies other than census tracts in each year by taking a weighted average of the tract-level values, using the number of renter-occupied housing units from the ACS 5-year summary file for the corresponding year as weight. For example, to estimate the ZRI for the large cities in 2015, a weighted average of the ZRI values for all tracts contained in each large city was calculated, using the number of renter-occupied housing units from the 2015 5-year summary file (which reflects a 2011-2015 average) as weight. To aggregate from census tracts to sub-counties (CPUMAs) and census-defined places (large cities, other cities or towns, and Census Designated Places), we used geographic crosswalks that were created by assigning each 2010 tract to the CPUMA and census-defined place containing the plurality of its 2010 population (from SF1 of the 2010 Census) by census block. All estimates were derived based on the same underlying 2010 census tract level data file for consistency. However, of this, estimates for geographies such as cities and counties will not align perfectly with the official ZRI estimates from Zillow, Inc., which can be accessed here. For more information on the methodology used by Zillow to develop the ZRI, see here. See the methodology page for other relevant notes.
- Values are for April 30th of each year and are not adjusted for inflation.
- Data are only reported for census-defined places (large cities, other cities or towns and Census Designated Places) for which at least three census tracts were assigned in the geographic crosswalks noted above, or for which one or two tracts were assigned but the vast majority (at least 80 percent) of the tract population(s) fell within the census-defined place based on 2010 block level population counts.