> And they traded at a 10% discount to A shares for over a year, because Chipotle was growing quickly, people were logging into their discount brokerage to buy

> And they traded at a 10% discount to A shares for over a year, because Chipotle was growing quickly, people were logging into their discount brokerage to buy CMG, and their brokerages were giving them CMG.A. The caveat is that this discount is only beneficial to a buy-and-hold strategy, in fact this discount was probably offset by the fact that CMG.B was less liquid than CMG.A and the spread was probably a bit higher as it was traded less often. Arbitrage opportunities are often too good to be true for a reason: selling CMG.B shares was probably the same trouble as buying them (before the split) so this market inefficiency was causing the 10% difference.