<p>Davidthefat, many adjunct positions used to be filled mainly by “trailing spouses,” by people whose main career was elsewhere, and by those who hadn’t finished their terminal degree. A lot of departments that didn’t have graduate programs use adjuncts instead of graduate instructors–so, whereas at, say , Berkeley, Yale, or UVA, your freshman comp teacher is likely to be somebody working on his or her PhD in the department, at, say, James Madison U. or American U., which don’t have big grad programs in English, that teacher will likely be an adjunct instead.</p>
<p>Things have changed since the recession; it’s much cheaper for a college to staff a course via adjuncts because the pay is dramatically lower and most of these positions lack benefits. Also, there’s rarely any job security, or any raises based on experience or performance; adjuncts typically have no say whatsoever in setting department policies. In recent years, tenure-track college-level teaching jobs in some fields have become so scarce that those who would previously have been qualified for them are forced to teach as adjuncts instead, unless they wish to leave academia altogether. It can be a pretty miserable way to make a living and the only people I know who seem to make it work for more than a few years are those who have a source of income elsewhere (for instance, a spouse who makes a good salary).</p>
<p>As to your other question: if you are a tenured professor already, you would ordinarily not apply for or be considered for untenured positions at another university. If a university does want you, it would normally offer immediate tenure as part of the “senior hire.” In other words, the hiring university would perform a regular tenure evaluation of the candidate (examination of their teaching, scholarship, professional service, etc. by a series of committees) prior to the offer being extended. There are occasional exceptions to this rule at the associate professor, or “middle” level. At most schools associate professor is a tenured rank but at a few, such as Carnegie Mellon and I believe MIT, it is an untenured rank. </p>
<p>The general effect of the tenure system, however, is to create what some people see as “stability” and others see as “rigidity”. On the one hand, once you get tenure, you are likely to have a job for life unless your school gets into financial difficulties, or you stop doing your job in a satisfactory way. This security can be a good thing for the institution–people who know they are going to be sticking around are often willing to pour uncompensated time and creativity into their university’s programs because they know they will benefit along with the rest of the community. On the other hand, if you don’t like where you are, there aren’t many places to move TO. There are many fewer senior positions than junior positions on offer, because most colleges’ senior faculty are just their junior faculty who have gotten promoted. And things get even more complicated when two academics are married or partnered and therefore need to be hired at the same time. So people tend to stay put, for better or worse, more than they do in industry.</p>