Low pay drives US academics to join union THOUSANDS of part-time US academics are joining trade unions, a growing trend that's boosting the ranks of organised labour and giving voice to teachers who complain about low pay and a lack of job security at some of the nation's top universities. The move to unionise at campuses follows a shift in hiring practices at colleges that rely more than ever on adjunct faculty to teach classes. Last month, adjuncts at Tufts became the latest to join the 2.1 million-member Service Employees International Union, which has been aggressively targeting college instructors. Adjuncts at Georgetown formed a union with SEIU in May, and part-time instructors at nearby American University joined the union last year. SEIU now represents more than 18,000 members at 10 colleges and universities, compared with 14,000 five years ago. The union is preparing to file for elections at more colleges in the Los Angeles, Seattle and Boston areas. Adjunct professors now make up more than half of all college faculty nationwide; in the 1970s, about 70 per cent of college instructors were tenured professors or on a track to tenure. Unlike full professors, most adjuncts earn just a few thousand dollars per class, with scant benefits and little job security. ``What started out decades ago as a way to supplement experience on college campuses by using adjunct professors has flipped," said Malini Cadambi, SEIU's national director of higher education. ``They are the majority of faculty labour on many campuses now, and their position has not improved. Kip Lornell, an adjunct music professor at George Washington University in the District of Columbia, has been teaching students for 25 years and is the author of 13 books on American music. He earns less than $US23,000 ($A24,383) a year teaching three classes at GWU. By contrast, a full professor at the university earns an average salary of $156,000 a year, according to data compiled by the American Association of University Professors. Kezar said critics of unions argue that they aren't always supportive of evaluations, which play an important role at many schools in the decision to rehire. Unions consider protecting teachers' interests first, and don't always consider student interests as strongly, she said. Unions argue that having well-compensated faculty with more training leads to better education for students.