UCLA is called a Public Ivy, and is ranked among the best public universities in the United States by major college and university rankings. This includes one ranking that has UCLA as the top public university in the United States in 2021. , 25 Nobel laureates, three Fields Medalists, and five Turing Award winners, and two Chief Scientists of the U.S. Air Force have been affiliated with UCLA as faculty, researchers, or alumni. Among the current faculty members, 55 have been elected to the National Academy of Sciences, 28 to the National Academy of Engineering, 39 to the Institute of Medicine, and 124 to the American Academy of Arts and Sciences. The university was elected to the Association of American Universities in 1974.