Some are chasing tenure-track positions of which there are fewer and fewer, but to get one requires staying active in academia. Some are industry professionals who may teach on the side for extra income or because they really want to teach.

Oversupply is part of it, but there's also the issue of Universities offering fewer and fewer full-time tenure track positions. This is a disservice to the students who are paying a fortune in tuition only to be taught by someone who, despite their best efforts, isn't given the resources to teach to the best of their ability.

You have to be careful when interpreting the numbers. Although the adjunct numbers are large, the number that are paid really low wages is considerably less. Adjunct faculty in business, law, etc. are often paid well. You can live pretty well on a full-time, non-tenure track wage if you are an economist. $80K and up is common.

In addition, you have a lot of adjunct faculty teaching for low compensation because they want to teach. Some work full time and want to keep their ties to the academic world. Some don't have a PhD so adjunct work is their only alternative if they want to teach at a research university. Some are taking time off to raise children, and with a well-paid spouse, they are in a position to teach for $4000 a class. Some are grad students trying to make enough to support themselves while writing a dissertation.

As for the others...good question. Many are holding out hope that one day they will get the magical tenure-track offer. It's wishful thinking in many humanities fields, to be honest.

Possibly because one enjoys it and finds one class per semester or year not to burdensome. Or one may be trying to break into the tenured world.

I taught briefly as a resume-builder. My wife did so to help out a friend who was taking over a class but not prepared to teach all of it; she later taught a restructured version by herself. Neither of us depended on it for a serious contribution to income.

But a friend of my wife's did the business of four classes at three colleges for a good while before she manage to catch on at a school prepared to offer her a tenure-track position. There is only so much work out there for an anthropologist.

I don't know. My wife taught as an adjunct briefly but we finally had to set the rule that she couldn't accept an adjunct contract that would lose money for us. That's right, they pay music adjuncts so little that gas for a 20-mile round trip, parking, etc. cost more than her pay. They could have made it work if they'd move classes so she was only on campus Tue/Thurs but they insisted on MWF and TueThur classes the same semester. Even when she taught an on-line class, she had to be on campus 2 days a week which we didn't factor into the cost.

Once you leave academia for an unrelated job, you're out for good. There's no way to get a tenure-track job when you've spent a couple years working in a different field, but that possibility still exists if you're teaching at a University, even as an adjunct.

They work for peanuts and a lottery ticket, not just peanuts.

I am just one data point, but here's how I ended up in a position similar to that described in the article.

I went to a "HYPS" school for grad school and postdoc (molecular biology). I wanted the typical tenure-track research position. At the end of my postdoc I had two interviews, one at at an ivy and the other at a very good state research university. Both jobs fell through for financial reasons (basically, both schools decided to withdraw funding for the position). At the time, my postdoc funding was running out and my sponsor suggested working at a startup in Cambridge. I took the startup job. It was a great job doing great research. However, after about 6 years, I decided that I needed to take care of aging parents and be closer to family. I quit the startup and moved to a place where there is essentially no biotech industry. There are some good schools in the area, but it's difficult to get back into the tenure-track research world as you get older (you can transition from industry to academia as an older person if you're "great", but I'm not great...I'm what I would call, "pretty good"...and a pretty good mid-to-late-40-year-old isn't getting tenure-track jobs at quality research universities). So, I'm geographically tied (by my choice). I work as an adjunct at a local university and as a full-time non-tenured faculty member at a local college (not a fancy school and no research). I also run a small consulting business. So, with 3 different jobs, I have cobbled together a salary that is similar to what I had in the biotech world (probably a little less than the biotech job).

A lot of the details in the Atlantic story rang true. I meet students from my adjunct position at the library (not by my car!). I keep almost everything in electronic format (including electronic scanning of student labs) so that I minimize lugging papers from school to school. The full-time faculty where I am an adjunct are quite nice, but you still get that vibe that you're a 2nd class citizen. If I want to write a student a recommendation, it's not a trivial endeavor to go to the adjunct school to get the proper letterhead paper. However, I've just downloaded the school's logo and made my own electronic version of their letterhead.

I think I'm in a better position than many of my colleagues. I'm still making decent money in aggregate. I think some of the adjuncts have very difficult lives, living check to check. And the ones who aren't very good at teaching (or who don't get along with the full-timers) feel like they're under constant threat of getting fired.

1) Sunk cost fallacy.

2) What else are you going to do when all your training is academic?