Bizible, a company created by former Bing/Microsoft adCenter staff, has put together an interesting analysis of local ranking factors in Google, after surveying 22 local business categories and 22 US cities, and searching Google for the given localized term (i.e. “Seattle photographer”).
"We grabbed the first 30 results in Google Local and all the local results from the integrated web results (1/3/5/7 packs, universal results, etc.) We then inspected each Places page for all of the ranking factors we could extract (see below for the complete list)," Bizible explains. "In total, we analyzed 477 queries, 14,309 individual search results, and 457,888 data points. We removed the seven queries that did not generate integrated local results, like 'Phoenix insurance.' Note that our analysis was performed before the recent 'Venice' Google search update in late February. We will run a followup study to see what has changed since then."
Venice involved improvements to ranking for local results, according to Google, who said in a blog post in February, "This improvement improves the triggering of Local Universal results by relying more on the ranking of our main search results as a signal."
For the universal or "integrated" results, as Bizible calls them, the top five ranking factors, according to the study, are:
1. Having the primary category match a broader category of the search category was associated with a 1.42 improvement in rank. For example, primary category is set to "restaurant" and the search category was "pizza."
2. Having the search category or a synonym in the business name was associated with a 0.64 improvement in rank.
3. Having the search category or a synonym in “at a glance” was associated with a 0.36 improvement in rank.
4. Having five or more Google reviews was associated with a 0.31 improvement in rank.
5. Having photos (atleast 1) was associated with a 0.25 improvement in rank.
The study lists a top 10 for pure local results:
1. Having five or more Google reviews was associated with a 1.47 improvement in rank.
2. Having the search city in “at a glance” was associated with a 1.42 improvement in rank.
3. Having the search category or a synonym in in review content was associated with a 0.97 improvement in rank.
4. Having the search category or a synonym in the business description was associated with a 0.85 improvement in rank.
5. Having the search category or a synonym in “at a glance” was associated with a 0.85 improvement in rank.
6. Having the primary category match the search category was associated with a 0.79 improvement in rank.
7. Having the search category or a synonym in in the business name was associated with a 0.75 improvement in rank.
8. Having a secondary business category that was a broader category than the search category was associated with a 0.68
improvement in rank. i.e. secondary category is “restaurant” when searching for “Seattle pizza.”
9. Having at least one photo was associated with a 0.66 improvement in rank.
10. Owner verified was associated with a 0.52 improvement in rank.
The study has a number of "surprsing takeaways" associated with the findings as well. I'd encourage you to read the report for additional insight.
Bizible says it looked at each ranking factor in isolation and accounted for variation in competitiveness across search terms. The firm says this study is only one in a series of five. The next ones will cover on-site optimization, citations, reviews, and in-bound links and off-site respectively.