Jack Welch introduced the vitality curve, also known as stack ranking, at GE to grade employees based on productivity. The model divides employees into top 20%, vital 70%, and bottom 10% based on performance reviews measuring characteristics like energy, decision-making, execution, and passion. Welch claimed using this "20-70-10" system contributed to GE's 28-fold increase in earnings. The approach ranks not just frontline workers but also managers as A, B, or C players according to their vision, drive, and ability to deliver results.