Accounting for July sales recorded in the first half of August, Zillow’s national existing home sales nowcast for July was revised down 1.9% from its projection earlier this month. Zillow now estimates 346.9k existing home sales in July. The previous nowcast for July was 353.4k sales. 

Zillow’s nowcast, explained

A nowcast is a projection of the very recent past or present. Most of Zillow’s monthly housing metrics — publicly available at zillow.com/data — have reflected known data at the close of the prior month. However, because a home sale typically takes weeks from when a seller accepts a buyer’s offer to when the sale officially closes and is recorded in the public record, home sales counts from Zillow and elsewhere traditionally report on a lag. 

Zillow’s existing home sales nowcast aims to eliminate this lag by using a statistical model incorporating past latency and average revision rates locally so that existing home sales are reported on the same cadence as most other metrics. 

Nowcast improvements

Beginning this month, Zillow is rolling out improvements to its nowcast to make the data more accurate and available even sooner. Using July sales data received through August 14, and refining the model to account for local changes in latency observed, improves the existing nowcast accuracy significantly in this mid-month update. 

Zillow’s differentiators

Zillow’s day-to-day as a listings portal enables better, supply sensitive forecasting. Zillow’s formal price and sales forecasts, for example, explicitly incorporate flows of new listings – or rather the lack thereof in today’s market. That contributed to keeping our home value expectations from turning negative when mortgage rates surged and demand dropped off two years ago, a price forecast that has so far held true. 

Zillow existing home sales numbers and forecasts stand out in other ways, too. Unlike some existing home sales estimates — including the National Association of Realtors’ existing home sales report, which is built from an opaque, weighted subsample of records maintained by multiple listing services — Zillow can size the housing market by actually counting sales. 

Zillow’s ever-updating database of property and transactions records – those underneath all those property pages on Zillow.com – is sourced directly from county offices, through direct feeds from MLSs, or updated by verified owners. 

This is a radical advantage in getting local and distinguishing trends from place to place, but the fantasy of national to local home sales reporting is only really possible after one big hurdle is passed: how to account for latency in sales data reporting. And Zillow just pushed a major update to do that even better.