Providing nutrition info on menus is fairly new–and menu labeling research is starting to roll in.
Personally, I don’t think looking at food ordering decisions in isolation is very informative. The effect of this particular “nudge” intervention is probably cumulative – like water dripping on a stone. It probably accumulates over time, after many exposures, and in combination with lots of other related messages that consumers get through other channels.
It also enables informed choices at that precise, elusive moment in time when someone finally makes the commitment to start making changes. And the value and importance of that is hard to overstate.
(There’s another benefit to mandatory nutrition labeling that often gets overlooked. Listing the # of carb grams is vitally important for anyone with diabetes who takes insulin, since most dosing is based on the # of carbohydrate grams consumed.)