Google's Possum Update: A Hidden Shift in Local Search Rankings

In September 2016, Google made significant changes to its local ranking systems without announcing them. The update, known as Possum, altered how the company's local filter works. This filter determines which business listings are eligible to appear in the three-result local pack and longer Local Finder list behind it.

Before Possum, the local filter primarily used shared telephone numbers and website domains to suppress duplicate listings. However, with Possum, Google extended the test to physical address and affiliation. Listings sharing a street address or that Google inferred as shared ownership began competing for a single slot even when phone numbers and domains differed.

The update affected professions that cluster, such as law firms in a single tower or medical specialists in one building. Sterling Sky's analysis documents the filter's current mechanics: listings are filtered on business name and URL, address, and proximity. The survivor is the listing with the strongest ranking authority for that specific query.

A study by Hawkins and BrightLocal analyzed 1,307 businesses tracking 14,242 keywords before and after the update. Nine percent of keywords showed a business entering the Local Finder for the first time, while 15% gained one or two positions. The wider search industry noticed little, as volatility trackers such as MozCast and Algoroo cover keyword sets with few three-pack queries.