Not so hard to figure out if you think about it. It's very effective discrimination against protected classes by using an unprotected class as cover.
I've read about this in any number of places and right here on Dkos "We don't hire the unemployed"
So what's the subtext? Why would any company put in their ads: "must be currently employed" as part of their criteria? In the diary referenced above, lots and lots of posters go down multiple garden paths and red herrings about how if someone was laid off, they didn't prove their value to the company, only the cream was still employed and people could be choosy, etc.etc.etc.
I think people are missing a very obvious point - What populations comprise a majority of the unemployed?
It wouldn't be minorities, the ill and disabled and the older populations, would it? But gee, those populations are "protected classes".
I got it! What if we just screen out "the unemployed"! That's not a protected class and we get to secretly and legally screen out the people we really want to screen out but wouldn't be able to otherwise except illegally.
Problem solved.
Now you know a great deal about the companies that would openly advertise a requirement like this.
This is a "soft discrimination".Not overt but all you have to do is think like an employer to see through it.
When things don't seem to make sense - they make sense to somebody for a reason you would never dream of.
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I would have made this a reply to the diary I linked to, but I thought this was overlong for a reply. I also thought the original diary was so big that this is an important point that would be lost in the shuffle.