Inferior good just means that demand increases as income goes down. Potatoes in your hypothetical are inferior, since if you have less money you can't afford steak and so buy more potatoes instead.
so that's what I mean, that term-of-art definition is intertwined with dependent variables of the definition of Giffen goods, so it would be no wonder if the ideas get tied together even if the concepts are not facially.
Terms of art annoy me (the legal profession and philosophy are full of them, overloaded (OOP definition) on preexisting words) because IANALinguist but I could play one on TV without rehearsing, so my point is, if you want to have a narrow morphology for a word, don't recycle a word that has broad meanings, invent a new word that is precise, like econ-inferior. Then at least when a person doesn't understand what you say, they will think to themselves "maybe I should look up the definition" as opposed to actually believing you said something different than you did.
Nobody can live on potatoes alone, you'd die. Nor can anybody live on steak alone. Neither good can be said to be precisely econ-inferior to another, only econ-inferior over some delta range of prices and/or time (and assuming demand, etc). But the whole question of Giffen goods is also valid only over some delta, so as long as they are different deltas, the definitions would not be in conflict (and vice versa all the variations of that).
I've studied econ at the graduate level at MIT after having taken it as an undergrad as well, and I have a degree in Finance, so I didn't mean to imply that I don't know what I'm talking about. But I know a lot of other topics as well and I've always objected to terms of art in one field being easily confused with terms from other areas, and hell if I can remember what an inferior good is 20 yrs later. My point was not that you didn't know what you were talking about; I joined in because between the two of you I replied to, I didn't think your discussion was benefiting the rest of HN as much as it could because many of those people have not taken any econ at all. I was trying to Econ 100 the discussion, without losing the flavor of what is interesting about Giffen goods; and I think that if researchers are going to "prove" that Giffen goods don't exist in aggregate (<-- not Macro term of art), they need to also address the obvious short term circumstances (as I tried to describe) where it's clear that the underlying principle is actually operating, whether it has an effect on market clearing or not, because people can go one extra week without meat, just can't do it forever.
Not trying to argue, just trying to clarify what I came upon. Econ theory I think is sound but requires many simplifying assumptions to teach and learn, and then when we talk about whether Giffen good actually exist or not it's easy to lose track of simplifying assumptions like "long term" or "substitution".
