The National Association of Realtors explains:

Each February, in conjunction with the release of final data for the previous calendar year, NAR Research conducts a normal review of seasonal activity and fine-tunes historic data for the past three years based on the most recent findings. For example, in data posted in February 2018 revisions have been made to monthly seasonally adjusted annual sales rates for 2015 through 2017, as well as the inventory month's supply data; most revisions are minor with little or no impact on previous characterizations of the overall market. There are no revisions to monthly home prices (single family and condo) or to raw inventory data (beyond normal prior-month revisions).

The Data Buffet extract contains 101 series, of which 18 are impacted: including total sales, single-family sales, condo sales, and inventory month's supply; SAAR sales data and NSA inventory month's supply; for the U.S. and census regions. Not all concept-geo combinations were revised.

• Concept codes: HXM, HX1M, HXCM, XHX?SUPM
• Geo codes: IUSA, C^^R