inquiry. The intent of tenure is to allow original ideas to be more likely to arise, by giving scholars the intellectual autonomy to investigate the problems and solutions as they see fit and to report their honest conclusions. However, it has also become a type of job security for professors. In North American universities and colleges, the tenure track has long been a defining feature of professorial employment, although it is less than universal. In North American universities, positions that carry tenure, or the opportunity to attain tenure, have grown more slowly than non-tenure-track positions, leading to a large "academic underclass". For example, most US universities currently supplement the work of tenured professors with the services of non-tenured adjunct professors, academics who teach classes for lower wages and fewer employment benefits under relatively short-term contracts. For those that are tenure track, it generally takes about seven years to earn tenure while working as an assistant professor. Tenure is determined by a combination of research, teaching, and service, with each factor weighted according to the values of a particular university, college or department. There is some evidence that professors that share more (e.g. via open access publications, open data, or open source hardware development) gain an advantage in obtaining tenure because they are cited more and can thus develop a higher h-index. This competition for limited resources could lead to ethically questionable behaviour. History in the United States 19th century In the 19th century, university professors largely served at the pleasure of the board of trustees of the university. Sometimes, major donors could successfully remove professors or prohibit the hiring of certain individuals; nonetheless, a de facto tenure system existed. Usually professors were only fired for interfering with the religious principles of a college, and most boards were reluctant to discipline professors. The courts rarely intervened in dismissals. In one debate of the Cornell University Board of Trustees in the 1870s, a businessman trustee argued against the prevailing system of de facto tenure, but lost the argument. Despite the power retained in the board, academic freedom prevailed. Another example is the 1894 case of Richard T. Ely, a University of Wisconsin–Madison professor who advocated labor strikes and labor law reform. Though the Wisconsin legislature and business interests pressed for his dismissal, the board of trustees of the university passed a resolution committing itself to academic freedom, and to retaining him (without