Is Yelp Actually Cleaning Up the Restaurant Industry? A Re-Analysis on the Relative Usefulness of Consumer Reviews

Social media provides the government with novel methods to improve regulation. One leading case has been the use of Yelp reviews to target food safety inspections. While previous research on data from Seattle finds that Yelp reviews can predict unhygienic establishments, we provide a more cautionary perspective. First, we show that prior results are sensitive to what we call “Extreme Imbalanced Sampling”: extreme because the dataset was restricted from roughly 13k inspections to a sample of only 612 inspections with only extremely high or low inspection scores, and imbalanced by not accounting for class imbalance in the population. We show that extreme imbalanced sampling is responsible for claims about the power of Yelp information in the original classification setup. Second, a re-analysis that utilizes the full dataset of 13k inspections and models the full inspection score (regression instead of classification) shows that (a) Yelp information has lower predictive power than prior inspection history and (b) Yelp reviews do not significantly improve predictions, given existing information about restaurants and inspection history. Contrary to prior claims, Yelp reviews do not appear to aid regulatory targeting. Third, this case study highlights critical issues when using social media for predictive models in governance and corroborates recent calls for greater transparency and reproducibility in machine learning.