Return on Advertising Spend (ROAS), or just Return on Ad Spend, is a marketing metric that measures the revenue generated by users acquired through a specific campaign, relative to the amount spent on their acquisition. In order to predict ROAS for a given paid cohort, an accurate forecast of their cumulative revenue is required. ROAS performance at specific dx (Days Since Install) milestones for past cohorts (such as d90) is commonly used to determine appropriate bids for ongoing spend.