Paul Krugman is pretty much done picking on Niall Ferguson for his widely-criticized takedown of President Obama and is moving on to Ferguson's publisher Newsweek. As Krugman sees it, the assertions Ferguson was throwing around would have never made it to print if the magazine had a proper fact-checking operation. How would this work? Krugman is happy to divulge the proprietary secrets of The New York Times' fact-checking system. "I supply a list of sources with each column submission," he wrote on his blog Tuesday. "For yesterday’s piece it looked like this":

$4.3 trillion: http://www.taxpolicycenter.org/numbers/displayatab.cfm?Docid=3301&DocTypeID=5 lines 2, 3 and 5

Ryan cuts: http://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: http://www.taxpolicycenter.org/numbers/displayatab.cfm?Docid=3337&DocTypeID=2

Ryan award: http://www.thefiscys.com/content/sen-kent-conrad-rep-paul-ryan-and-gov-mitch-daniels-named-2011-fiscy-award-recipients

Baseline: http://www.latimes.com/news/nationworld/nation/la-na-ryan-20120817,0,1246452.story

That's step 1. Step 2 is tussling it out. "Each time I send in a column draft, the copy editor runs quickly through the citations, making sure that they match what I assert," he writes. "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."

There you go! Now you knows what it's like to edit Paul Krugman. He ends the blog post by asking if Newsweek is going to address the factually-challenged aspects of Ferguson's piece. But he may have missed the boat on this one. On its fact-checking policies, here's Newsweek's response via Politico's Dylan Byers:

"We, like other news organisations today, rely on our writers to submit factually accurate material," Newsweek spokesman Andrew Kirk told POLITICO.

And how about issuing a correction? The magazine says this is a matter of opinion:

"This is not the opinion of Newsweek, this is the opinion of Niall Ferguson," [executive editor Justine] Rosenthal said.

As The Atlantic's Ta-Nehisi Coates puts it "Newsweek has unwittingly outsourced its fact-checking to the web." That puts it squarely in your hands, Paul.