One of Zillow’s most cited metrics is ZHVI, the Zillow Home Value Index. 

It tells us the typical home value in a given geography (metro area, city, ZIP code, etc.), now and over time. For general information about ZHVI, please refer to this methodology guide.

When citing ZHVI, it’s important to understand how it works, including its cuts (which are like “flavors”) and naming conventions, and how to calculate common statistics with it. 

Here’s an overview:

What to Call ZHVI

ZHVI represents the “typical” home value for a region. It’s calculated as a weighted average of the middle third of homes in a given region. 

When referring to the ZHVI dollar amount, it should be designated as the “typical home value for the region.” It is NOT the “median home value.”

ZHVI Cuts

ZHVI is calculated in a variety of cuts, consisting of different home types and adjustments. No one cut is more correct than another. The version that works best for each user depends on the use case. 

These cuts are available on Zillow Research’s data page, zillow.com/data.

Smoothed, Seasonally Adjusted ZHVI

The most-cited ZHVI is the all homes, middle tier, smoothed and seasonally adjusted cut. It is used by Zillow for most consumer-facing presentations of the ZHVI, such as on our Home Details Pages (the address page for most U.S. homes) and Home Values Pages (which shows ZHVI for various regions).This cut represents the middle of the market for all homes. In Zillow’s Econ Data API, this ZHVI cut is keyed with a cutTypeKey of uc_sfrcondo_tier_0.33_0.67_sm_sa.

Raw ZHVI

Zillow’s monthly Market Reports use the all homes, middle tier, raw cut of ZHVI. This version shows shifts in market conditions  more quickly than the smoothed, seasonally adjusted cut because it does not smooth changes over the preceding three months. That can also result in more “noise” in the results from month to month. 

In Zillow’s Econ Data API, this ZHVI cut is keyed with a cutTypeKey of uc_sfrcondo_tier_0.33_0.67.

Zillow Home Value Forecast

The Zillow Home Value Forecast (ZHVF) uses the middle-tier version of ZHVI. Both raw and smoothed, seasonally adjusted versions of ZHVF are available. 

Other ZHVI Cuts

ZHVI is also available for the top tier (homes within the 65th to 95th percentile range for a given region) and bottom tier (homes within the 5th to 35th percentile range for a given region) of each region. Zillow also publishes ZHVI for all single-family residences, for condo/co-ops, and for all homes with 1, 2, 3, 4 and 5+ bedrooms.

ZHVI Release Schedule

ZHVI and ZHVF for a given month are published on the Econ Data API within weeks of that month ending. 

When data are released, the last valid point for ZHVI is the end of the month prior to the release month (e.g., ZHVI for January 2023 will be published in February 2023). The first month of ZHVF is the end of the month of the release month (e.g., the version of ZHVF published in February 2023 is projecting home values from February 28, 2023 forward).

The time point the ZHVI/ZHVF represents is designated in the timePeriodEndDateTime key. 

Calculating Historical and Forecasted Growth

Yearly growth rates for ZHVI are always calculated same month to same month. For example, if you wish to display how much home values have changed over the prior year (in percentage terms), you use the formula:

\[100* \frac{ZHVI(This Month Current Year) – ZHVI(This Month Last Year)}{ZHVI(This Month Current Year)}\]

To calculate the forecasted growth for the coming year, you use the same formula, but substitute  ZHVF for ZHVI for one point:

\[100* \frac{ZHVF(This Month Next Year) – ZHVI(This Month Current Year)}{ZHVI(This Month Current Year)}\]

Here are some example scenarios:

Let’s take a dummy example region, 12345. You want to display how much home values have grown for region 12345 over the past year, and how much they are forecasted to grow in the coming year. It is currently February 2023, after January 2023 data has been released.

ZHVI growth over the past year, after monthly publication:

\[Growth = 100* \frac{ZHVI(Jan-31-2023) – ZHVI(Jan-31-2022)}{ZHVI(Jan-31-2022)}\]
  

ZHVI forecasted growth over the next year, after monthly publication: 

\[Growth = 100* \frac{ZHVF(Jan-31-2023) – ZHVI(Jan-31-2022)}{ZHVI(Jan-31-2022)}\]

ZHVI growth over the past year, before monthly publication: 

There is a slight time lag due to the monthly publication schedule; January numbers have not been published yet. As such, the growth should be calculated relative to December numbers:

\[Growth = 100* \frac{ZHVI(Dec-31-2022) – ZHVI(Dec-31-2021)}{ZHVI(Dec-31-2021)}\]

ZHVI forecasted growth over the next year, before monthly publication: 

There is a slight time lag due to the monthly publication schedule; January numbers have not been published yet. As such, the growth should be calculated relative to December numbers:

\[Growth = 100* \frac{ZHVF(Dec-31-2022) – ZHVI(Dec-31-2021)}{ZHVI(Dec-31-2021)}\]