A study titled "Generative AI as a Qualification-Biased Technological Change: Evidence from U.S. Resume and Hiring Data," conducted by Harvard researchers Seyed M. Hosseini and Guy Lichtinger, sheds light on how generative AI is reshaping the labor market through a qualification-based stratification process. Drawing on extensive data from Revelio Labs, which encompasses 285,000 U.S. firms, 62 million employees, and 245 million job postings spanning from 2015 to 2025, the research uncovered significant trends following the ChatGPT boom in early 2023. Specifically, companies that embraced AI technologies experienced a relative 7.7% drop in entry-level hiring over six quarters, contrasting with a 2.1% increase in senior-level positions. The main factor behind this shift was a decrease in recruitment rather than widespread layoffs. The wholesale and retail sectors were particularly hard-hit, with entry-level hiring plummeting nearly 40% on a quarterly basis. The impact on employment varied according to educational background, following a U-shaped pattern: graduates from top-tier (Tier 1) and average universities (Tier 5) were relatively unscathed, whereas those from upper-middle-tier institutions (Tier 2-3) faced the most significant disruptions. To establish a robust causal relationship, the study utilized a Difference-in-Differences (DiD) methodology, comparing firms that posted job listings with keywords such as LLM, Prompt Engineer, and GenAI (treatment group) against those that did not adopt AI technologies (control group).