This is the worst thing to happen to ETFs

ETFs were a great invention until they fell into the hands of retail investors and advisers.

That’s the tongue-in-cheek lesson I am drawing from two recent research studies into the real-world performance of ETFs and portfolios of ETFs. The studies’ unifying theme is that, by giving investors the ability to trade into and out of the market at any time, ETFs enable investors to indulge their worst instincts.

The…