When a core ingredient in an iconic product gets swapped out, it’s rarely a marketing experiment. Ya don’t put chicken in a Big Mac by accident. Lately, I’ve been seeing billboards for the Chicken Big Mac. On the surface, it looks like a creative limited-time promotion. Something new. Something fun, right? But check out the big picture and it starts to look like something else. Beef prices have hit record highs in recent weeks, driven by shrinking cattle herds, drought conditions, and rising...