Vast literatures as mud moats


Over at Noah Smith's site:

[T]he demand to "go read the vast literature" could also be eminently unreasonable. Just because a lot of papers have been written about something doesn't mean that anyone knows anything about it. There's no law of the Universe stating that a PDF with an abstract and a standard LaTeX font contains any new knowledge, any unique knowledge, or, in fact, any knowledge whatsoever. So the same is true of 100 such PDFs, or 1000.
There are actual examples of vast literatures that contain zero knowledge: Astrology, for instance. People have written so much about astrology that I bet you could spend decades reading what they've written and not even come close to the end. But at the end of the day, the only thing you'd know more about is the mindset of people who write about astrology. Because astrology is total and utter bunk.
But astrology generally isn't worth talking or thinking about, either. The real question is whether there are interesting, worthwhile topics where reading the vast literature would be counterproductive – in other words, where the vast literature actually contains more misinformation than information.
There are areas where I suspect this might be the case. Let's take the obvious example that everyone loves: Business cycles. Business cycles are obviously something worth talking about and worth knowing about. But suppose you were to go read all the stuff that economists had written about business cycles in the 1960s. A huge amount of it would be subject to the Lucas Critique. Everyone agrees now that a lot of that old stuff, probably most of it, has major flaws. It probably contains some real knowledge, but it contains so much wrong stuff that if you were to read it thinking "This vast literature contains a lot of useful information that I should know," you'd probably come out less informed than you went in.
More here.