So markets can only be (perfectly) efficient or competitive, not both at the same time. Largely theoretical but it tracks common sense!

The title on this HN submission is just wrong. Click on the link and find out.

The title is wrong but you’re also wrong. Read the abstract of the paper. Here’s the relevant section:

> Combined with Maymin (2011), who proved that market efficiency requires P = NP, this yields a fundamental impossibility: markets can be informationally efficient or competitive, but not both.

isn't that what they're saying with "not both at the same time"? the papers both have opposite signs, one has != and the other has =

Without the braces around the perfectly I would have understood it... yeah, I think I was misinterpreting what he meant to say

Assuming the original result is correct, isn’t the linked paper simply a corollary?

The newer paper expands on the work of the former.

In a P=NP world, it still takes only one uninformed participant to make the market inefficient. I don't think the implication is bidirectionally true unless you assume every single player is rational, infinitely smart, and has access to the same set of information.

Its game theory so perfect play is assumed. Spherical cows and all that