To me it is not whether such a law would be justified, but whom it would hurt and whom it would hurt.
Anything that makes hiring the bottom end of the labor pool more expensive will decrease the amount of that pool that is hired. There are some who claim studies that show this is not true. I claim these studies are dopey. If it were not true that raising minimum wage causes fewer from the bottom to tbe hired, why not raise it to $20/hr? $50/hr? Can anybody who even bothers to fully oxygenate their blood fail to see that if you raised the minimum wage to $50/hour there would be massive unemployment? Well tickling the wage down around only $7, $8, or $9/hr is the same thing, only writ small enough so that what is blisteringly obvious with bigger numbers can be missed by people who want to pretend it isn't there.
If the minimum wage is raised, it will LOOK successful in the sense that the people who still have jobs, who still get jobs, will be paid more. Guess who will lose jobs? The hardest to hire. The least capable.
So if you feel more comfortable pretending that everybody can work and make a certain amount of money, AND it is easier for you to ignore the people that can't get jobs than to pretend that $7/hour is enough, then keep going down this road. Put the hardest to hire out of the labor force entirely, pay for them on welfare, and pretend they don't exist while congratulating those that still do have jobs on what a good job you did for them.
Note: Originally posted in Discussion, edited to take comments there into account.
Yes, politics, boo hiss. In my defense, the topic of this post cuts across usual tribal affiliations (I write it as a liberal criticizing other liberals), and has a couple strong tie-ins with main LessWrong topics:
The issue is this: recently, I've seen a meme going around to the effect that companies like Walmart that have a large number of employees on government benefits are the "real welfare queens" or somesuch, and with the implied message that all companies have a moral obligation to pay their employees enough that they don't need government benefits. (I say mention Walmart because it's the most frequently mentioned villain in this meme, but others, like McDonalds, get mentioned.)
My initial awareness of this meme came from it being all over my Facebook feed, but when I went to Google to track down examples, I found it coming out of the mouths of some fairly prominent congresscritters. For example Alan Grayson:
Or Bernie Sanders:
Now here's why this is weird: consider Grayson's claim that each Walmart employee costs the taxpayers on average $1,000. In what sense is that true? If Walmart fired those employees, it wouldn't save the taxpayers money: if anything, it would increase the strain on public services. Conversely, it's unlikely that cutting benefits would force Walmart to pay higher wages: if anything, it would make people more desperate and willing to work for low wages. (Cf. this this excellent critique of the anti-Walmart meme).
Or consider Sanders' claim that it would be better to raise the minimum wage and spend less on government benefits. He emphasizes that Walmart could take a hit in profits to pay its employees more. It's unclear to what degree that's true (see again previous link), and unclear if there's a practical way for the government to force Walmart to do that, but ignore those issues, it's worth pointing out that you could also just raise taxes on rich people generally to increase benefits for low-wage workers. The idea seems to be that morally, Walmart employees should be primarily Walmart's moral responsibility, and not so much the moral responsibility of the (the more well-off segment of) the population in general.
But the idea that employing someone gives you a general responsibility for their welfare (beyond, say, not tricking them into working for less pay or under worse conditions than you initially promised) is also very odd. It suggests that if you want to be virtuous, you should avoid hiring people, so as to keep your hands clean and avoid the moral contagion that comes with employing low wage workers. Yet such a policy doesn't actually help the people who might want jobs from you. This is not to deny that, plausibly, wealthy onwers of Walmart stock have a moral responsibility to the poor. What's implausible is that non-Walmart stock owners have significantly less responsibility to the poor.
This meme also worries me because I lean towards thinking that the minimum wage isn't a terrible policy but we'd be better off replacing it with guaranteed basic income (or an otherwise more lavish welfare state). And guaranteed basic income could be a really important policy to have as more and more jobs are replaced by automation (again see gwern if that seems crazy to you). I worry that this anti-Walmart meme could lead to an odd left-wing resistance to GBI/more lavish welfare state, since the policy would be branded as a subsidy to Walmart.