To answer these questions, we turned to the data—in this case, anonymized, aggregated US consumer spending data captured via credit cards, debit cards, and bank transfers, which has become a popular tool for analyzing high-growth startups. For the Marketplace 100, we use data from a company called Second Measure, a firm that analyzes billions of purchases to track real-time consumer behavior and relative sales across 4,500 merchants.

https://a16z.com/2020/02/18/marketplace-100/