This report was produced by "The School Librarian Investigation: Decline or Evolution?" (SLIDE), a research project funded by a Laura Bush 21st Century Librarian grant from the Institute for Museum and Library Services to Antioch University Seattle. It studied the employment status of school librarians in the United States from 2009-10 through 2018-19. The analysis examined data from all 50 states and D.C. as well as over 13,000 local school districts. The data are collected annually by the National Center for Education Statistics via its Common Core of Data program. The findings document an almost 20 percent loss of school librarians between 2010 and 2019, the most recent data available at the time. Further analysis uncovered gross inequities in access to school librarians across the U.S. Districts with more students living in poverty, more minority students, and more English language learners were less likely to have librarians than districts with fewer such students. Other notable findings: (1) Three out of 10 districts had no librarians in any of their schools; (2) More than 4.4 million students in high-poverty (50%+) districts had no librarians; (3) Almost 3.1 million students in predominantly Hispanic districts were without school librarians; (4) Almost 4.8 million students in predominantly non-white districts were without school librarians; (5) Smaller and rural districts were more likely to have no librarians than larger and suburban districts; and (6) Nine out of 10 charter school districts had no school librarians. The study questions the conventional wisdom that losses of school librarians are explained by school funding cuts. During the decade studied, employment for other types of educators increased--sometimes dramatically--while librarian employment alone declined steadily. Also, districts with the most librarians relative to schools were those that spent the most, and the least, per pupil. Stronger librarian staffing was also found in states that had staffing mandates, whether they were enforced or not, and in states that had more institutions of higher education preparing school librarians. These findings provide solid evidence of inequities nationally, by state, and based on characteristics of local districts and their student demographics. It also has implications for the future preparation of school librarians and for school districts attempting to improve educational equity for their K-12 students. [This report was co-prepared by Antioch University Seattle.]