What does “CAR-RT PRESORT” mean on junk mail?

Dear Cecil: I’m getting a lot of junk mail these days, and I notice that on many of the computer labels there is the same series of symbols, in my case CAR-RT PRESORT **CR37. At first, I thought it was a code the junk mail places were using to determine my marketing profile or something. But when I noticed the same code on my IRS label, I wasn’t so sure. What is the meaning of this code? Can you give me a letter-perfect answer and stamp out my ignorance? If you can you’ll be my male #1. Eugene S., Evanston, Illinois

Cecil replies:

Frankly, Eugene, I have no desire whatever to be your male #1. But don’t think I don’t appreciate the thought. “CAR-RT” means “carrier route,” and “carrier route presort” means pretty much what it sounds like. The bulk (i.e., junk) mailers sort out their letters into separate stacks for each mail carrier before turning them over to the Postal Service. In return they get a 30 percent lower rate. The USPS, needless to say, supplies the mailers a list of what addresses each carrier route serves. The result is the ever-burgeoning collection of trash you find in your mailbox every day.

Cecil Adams

Send questions to Cecil via cecil@straightdope.com.