Top 20 cities for free candy? Check Zillow's 'Trick-or-Treat Index'

Annual list based on home values, population density, walkability, crime

San Francisco, Boston and Honolulu are the best bets for productive trick-or-treating this year, based on the latest annual index released this week by online real estate company Zillow.

The Zillow Trick-or-Treat Index is based on four equally weighted data points: the company’s Zillow Home Value Index, which is an aggregation of the company’s home-value estimates for each city area; walkability data by Walk Score (www.walkscore.com); population density statistics, and local crime data from RelocationEssentials.com.