Though corporate finance researchers have long considered firm diversification a topic of interest, the lack of reliable data about firms’ cross-industry activities has made the area difficult to study. Recent advances in text-based analysis has bolstered renewed efforts in this direction. Inspired by the work of Hoberg and Phillips (2024) in analyzing 10K filings, I have created a set of industry classification algorithms designed to measure the extent of firm diversification. I show that lifetime diversification trajectories vary significantly between firms in different industries, as well as along other firm characteristics of interest.