For strong form efficiency (which requires markets perfectly reflect all available information) -
You would have trouble finding people who still believe in strong form efficiency.
The weak form paper above cites several papers that go into why strong form efficiency is impossible. There are formal proof versions around. In practice, even empirical studies of strong form efficiency haven't supported it either - it's just very easy to find practical counterexamples.
I skimmed this paper and it seems to be exceptionally bad. The proof sketch offered is that a winning strategy can be verified quickly, but finding a winning strategy requires searching over 3^n possible strategies.
But this assumes that brute force is the only possible way to find a winning strategy, and thus proves far too much. A similar argument would prove that sorting is NP hard, if you start by the assumption that the only way to sort data is by trying every possible permutation.
I may be wrong, but I'm pretty sure any time you claim to have a proof that a problem is NP complete, but your proof doesn't include a reduction, you're doing it wrong.
(The paper does offer what it calls a reduction to 3-sat
, but it's completely hand-wavy, and I can't even understand the intuition behind it at all.)
For strong form efficiency (which requires markets perfectly reflect all available information) - You would have trouble finding people who still believe in strong form efficiency. The weak form paper above cites several papers that go into why strong form efficiency is impossible. There are formal proof versions around. In practice, even empirical studies of strong form efficiency haven't supported it either - it's just very easy to find practical counterexamples.