Prior to the passage and subsequent enforcement (through litigation) of the National Historic Preservation Act of 1966 and other laws, most archaeologists, historians, and other historic preservation specialists were employed primarily in the field of academia, working at universities or other places of higher learning. However, since the passage of the NHPA, ever-increasing numbers of these professionals are employed in support of the cultural resources management industry. Large public works projects often require that teams of archaeologists perform limited excavations in order to properly inventory buried archaeological remains and assess their eligibility for the National Register of Historic Places. This industry has also allowed a larger swath of individuals to participate in archaeology and history as, unlike in the academic arena, a PhD is not required to earn a professional livelihood.