Looking at the comments on my Niall Ferguson takedown (see Ezra Klein, Matthew O’Brien, James Fallows, and Noah Smith for more), I found my memory jogged about a point I’ve been meaning to make about the nature of error in economics.

It seems to me that when readers declare that some piece of economics commentary is “wrong”, they often confuse three different notions of wrongness, which are neither intellectually nor morally equivalent.

First, there’s the ordinary business of expressing a view about the economy that the reader disagrees with – e.g., “Krugman is wrong, because the government can’t create jobs”; or, if you prefer, “Casey Mulligan is wrong, because we’re suffering from demand problems, not supply problems.” Obviously it’s OK to say things like this, and sometimes the criticism is correct. (I’m not wrong, but Mulligan is!) But equally obviously, there’s nothing, er, wrong about being wrong in this sense: people will disagree, and that’s legitimate.

Second, and much less legitimate, is the kind of wrongness that involves making assertions that are logically or empirically indefensible. I’d put the Cochrane/Fama claims that government spending can’t increase demand as a matter of accounting in this category; this is a basic conceptual error, which goes beyond mere difference of opinion. And economists who are wrong in this sense should pay a professional price.

That said, I don’t think it’s realistic to expect the news media to be very effective at policing this kind of wrongness. If professors with impressive-sounding credentials spout nonsense, it’s asking too much of a newspaper or magazine serving the broader public to make the judgment that they actually have no idea what they’re talking about.

Matters are quite different when it comes to the third kind of wrongness: making or insinuating false claims about readily checkable facts. The case in point, of course, is Ferguson’s attempt to mislead readers into believing that the CBO had concluded that Obamacare increases the deficit. This was unethical on his part – but Newsweek is also at fault, because this is the sort of thing it could and should have refused to publish.

Now, I don’t expect a publication that responds to daily or weekly news to do New Yorker-style fact checking. But it should demand that anyone who writes for it document all of his or her factual assertions – and an editor should check that documentation to see that it actually matches what the writer says.

That’s how it works at the Times, or at least how it works for me. I supply a list of sources with each column submission; for yesterday’s piece it looked like this:

$4.3 trillion: //www.taxpolicycenter.org/numbers/displayatab.cfm?Docid=3301&DocTypeID=5 lines 2, 3 and 5 Ryan cuts: //www.cbpp.org/cms/index.cfm?fa=view&id=3723 (I count his Medicaid cuts relative to current policy, not policy including Obamacare) Disproportionate benefits at top: //www.taxpolicycenter.org/numbers/displayatab.cfm?Docid=3337&DocTypeID=2 Ryan award: //www.thefiscys.com/content/sen-kent-conrad-rep-paul-ryan-and-gov-mitch-daniels-named-2011-fiscy-award-recipients Baseline: //www.latimes.com/news/nationworld/nation/la-na-ryan-20120817,0,1246452.story

Each time I send in a column draft, the copy editor runs quickly through the citations, making sure that they match what I assert. Sometimes the editor feels that I go further than the source material actually justifies; in that case we either negotiate a rewording, or drop the assertion altogether. Oh, and weasel-wording isn’t acceptable – implying something the facts don’t support is no more OK than stating it outright.

And despite all this, sometimes an error slips through. In that case, the response is a print correction.

We know what Ferguson is going to do: he’s going to brazen it out, actually boasting about the deftness with which he misled his readers. But what is Newsweek going to do?