Joe Stiglitz has an Opinionator piece arguing that inequality is a big factor in our slow recovery. Joe is an insanely great economist, so everything he says should be taken seriously. And given my political views and general concerns about inequality, I’d like to agree.

But — you knew there was a “but” coming — I’ve thought about these issues a lot, and haven’t been able to persuade myself that this particular morality tale is right.

It’s worth noting that two of Joe’s four points aren’t really about the current recovery. He argues that high inequality is causing huge waste of human talent, because the poor and increasingly the middle class lack access to good education; and I agree. He also argues that inequality fosters financial crisis, and I agree with that too.

But we’re talking about the financial crisis aftermath, not the crisis itself. What role does inequality play?

First, Joe offers a version of the “underconsumption” hypothesis, basically that the rich spend too little of their income. This hypothesis has a long history — but it also has well-known theoretical and empirical problems.

It’s true that at any given point in time the rich have much higher savings rates than the poor. Since Milton Friedman, however, we’ve know that this fact is to an important degree a sort of statistical illusion. Consumer spending tends to reflect expected income over an extended period. If you take a sample of people with high incomes, you will disproportionally include people who are having an especially good year, and will therefore be saving a lot; correspondingly, a sample of people with low incomes will include many having a particularly bad year, and hence living off savings. So the cross-sectional evidence on saving doesn’t tell you that a sustained higher concentration of incomes at the top will lead to higher savings; it really tells you nothing at all about what will happen.

So you turn to the data. We all know that personal saving dropped as inequality rose; but maybe the rich were in effect having corporations save on their behalf. So look at overall private saving as a share of GDP:

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The trend before the crisis was down, not up — and that surge with the crisis clearly wasn’t driven by a surge in inequality.

So am I saying that you can have full employment based on purchases of yachts, luxury cars, and the services of personal trainers and celebrity chefs? Well, yes. You don’t have to like it, but economics is not a morality play, and I’ve yet to see a macroeconomic argument about why it isn’t possible.

Joe also argues that high income inequality depresses tax receipts, fueling fiscal fears. Again, I have trouble with this point: our tax system isn’t as progressive as it should be, but it is at least mildly progressive even when you take state and local taxes into account. So I don’t know where this is coming from.

I wish I could sign on to this thesis, and I’d be politically very comfortable if I could. But I can’t see how this works.