[blargey]

That's a terrible example - how much room for improvement is left for the VOO-tier sensible, simple investment vehicles that matter to normal people with their monthly 401k buys? 1/10th of a BP? 1/100th? Is Jane Street hiring to chase diminishing returns to such broadly relevant, already-efficient markets, or to cook up new market-manipulation schemes of the sort that got them kicked out of India, that are antithetical to the market integrity such firms are supposed to provide?

The notion that efficient markets require firms like Jane Street to endlessly chase extra "edges" is a false dichotomy. The world would be a better place if intelligent people made more of the concrete products and services that get priced, than if they chased butterflies to expose that price one minute earlier to concentrate ever-more ephemeral, irrelevant arbitrage opportunities into their own little house like a Maxwell's Demon of the stock market.