Devils Advocate: Ah! but now you have a budget, you need to track it to make sure you're sticking to it - how do you know if you're spending 50% less on eating out this month if the data arn't there in-front of you to check?
I felt like the parent comment didn't meant 50% exactly, just an approximation. So, if it were me, I'd just keep that in mind when deciding to go out to eat.. After 1 or 2 months it's easy to see if I'm on track to the ~50% or not and adjust accordingly.
I guess he'll find out next year when he repeats the exercise :)
True. My pragmatic approach: 50% of the times I have the urge to eat out, don't do it :)