In the report To Err is Human (1999), the National Academy of Medicine called for national action to improve patient safety in hospitals. The report concluded that improving nurse work environments—assuring adequate nurse staffing and supporting nurses’ ability to care for patients—was critical to these efforts. Two decades later, have nurse work environments improved, and has that had a noticeable impact on patient safety? To find out, a research team led by LDI Senior Fellow Linda Aiken, PhD, RN surveyed more than 800,000 patients and 53,000 nurses in 535 hospitals in 2005, and again in 2016.