In North America, an adjunct professor, also known as an adjunct lecturer or adjunct instructor (collectively, adjunct faculty), is a professor who teaches on a limited-term contract, often for one semester at a time, and who is ineligible for tenure. Increase in adjunct labor Colleges and universities began to employ greater numbers of non-tenure-track faculty in the 1970s. In 1975, adjuncts represented roughly 24% of instructional staff at degree-granting institutions, whereas in 2011 they represented over 40% of instructional staff. Various explanations have been given for this shift. Some "trace the practice of hiring part-time instructors to a time when most schools didn’t allow women as full professors, and thus adjunct positions were associated with female instructors from the start." Many non-tenure-track faculty were married to full-time, tenure-track professors, and known as "the housewives of higher education." The majority of non-tenure-track professors are still women. Some have argued that the increase in the use of non-tenured faculty is the result of “financial pressures, administrators’ desire for more flexibility in hiring, firing and changing course offerings, and the growth of community colleges and regional public universities focused on teaching basics and preparing students for jobs.” Others have argued that universities hire non-tenure-track faculty to "offset ... administrative bloat with cheaper labor" to the detriment of students: "while college tuition surged from 2003 to 2013 by 94 percent at public institutions and 74 percent at private, nonprofit schools, and student debt has climbed to over $1.2 trillion, much of that money has been going to ensure higher pay for a burgeoning legion of bureaucrats." Paying some instructors less than others for the same teaching duties may be illegal. Compensation and academic use In past decades, adjunct faculty helped universities and colleges expand the range of their course offerings to prospective and existing students. In this respect, adjuncts can also be used to inform the predominantly theoretical, and therefore somewhat limited, focus of full-time academics with the more pragmatic perspective of those who actually practice a given discipline in business, government or nonprofit organizations, akin to a professor of practice. For instance, as of the early 1990s Marvin Kaye, a prolific fiction author, editor and anthologist, also worked as part-time adjunct faculty of creative writing at New York University Another example is Edward H. Shortliffe, a pioneer in medical informatics, who was an adjunct faculty member at Columbia College of Physicians and Surgeons