I'm on the hiring committee for an assistant professor position in the economics department at Towson. We have a couple hundred applications to review and I know that many applicants apply to over 100 jobs. So how can I tell as a reviewer who is really interested in the job and who is just sending their application in. I care, because as part of the committee we will decide on a couple dozen people to interview in San Diego.
Luckily economists have devised a clever solution to help make sure candidates who really want a job can indicate it. Each job candidate is allowed 2 schools to signal. All that happens is the hiring school receives an e-mail of all the candidates who used their signal at their school. The idea is that you can show you really care about a couple of jobs, but if a school doesn't receive a signal it doesn't show you don't care because you only can send 2. More info here
When I applied for my job at Towson, I sent one of my signals to Towson. I'm not sure if it made a difference in me getting an interview. I sent the signal because I really wanted to move to the DC area to be with my wife and the job seemed like a really good fit given my research and teaching interest. I wasn't sure if my application would stand out enough given my background. On the other hand I did not send a signal to a job at a well known small liberal arts school in the midwest, because I thought my record with 1 year teaching at Beloit (a similar school) and an undergrad at Grinnell would be enough to get me an interview. I was right I did get an interview and an on campus interview with the well known SLAC (although not a job offer). The SLAC department chair did notice they didn't receive a signal from me, although this was more pointed out by the Dean and the Chair had explained to the Dean that I probably believed I had already shown enough interest in teaching at SLAC given my experience and didn't need a signal. I think the chair was right (given I got the interview).
In the past based on talking to my colleagues a signal will give your application a little more attention. I think it might also help if departments are worried that a candidate won't take a job, this could also help.
I think signaling is good particularly since there is a non-zero change that it helped me get a great job.