Since the second half of the twentieth century, independent research has become a central focus of the Academy. In the late 1950s, arms control emerged as one of its signature concerns. The Academy also served as the catalyst in establishing the National Humanities Center in North Carolina. In the late 1990s, the Academy developed a new strategic plan, focusing on four major areas: science, technology, and global security; social policy and education; humanities and culture; and education. In 2002, the Academy established a visiting scholars program in association with Harvard University. More than 75 academic institutions from across the country have become Affiliates of the Academy to support this program and other Academy initiatives.