It's from this new book by Larry Bartels, an economist at Princeton.
You'll notice I touched up the original by using the font feature in MS Paint to overlay new fonts on the scanned version, which was a little rough. I did my best to align the values with the hash marks, and I obviously did not move the data points, just darkened the lines a little.
Krugman's blog yesterday noted that the lack of a mechanism is daunting to some who would challenge the "correlation vs. causation" issue here.
