How the Map Pack Ranks: Relevance, Distance and Prominence
Google describes local ranking through three factors: relevance, meaning how well a profile matches what was searched; distance, meaning how far the business is from the searcher or the searched area; and prominence, meaning how well known and well regarded the business is. Only one of those is fixed. Relevance and prominence are both directly improvable, and most businesses have barely started on either of them. The ones that work on both are the ones that stay in the pack.
Relevance is largely a completeness problem. The primary category carries substantial weight and is frequently chosen carelessly, sometimes years ago by someone who has since left. Secondary categories, the services list, product entries, attributes and the business description all give the system more to match against. A profile listing twenty specific services can be relevant to twenty specific queries. A profile with one category and a phone number can be relevant to one.
Prominence is built from signals outside the profile: review volume, rating and recency, citation consistency, links and mentions from other sites, and the authority of the website attached to the listing. This is where local SEO and conventional SEO stop being separate disciplines. A site with strong technical foundations, real content and earned links makes its associated listing more prominent, which is why local SEO, conventional SEO and the underlying web design should be run as one program rather than bought from three suppliers.