What's the difference between an under-developed country and a developing one?

The answer of course is in the cultural baggage we attach to the words. Under-developed is like under-fed, under-resourced, under-appreciated, under-weight, under-represented, they all suggest problems and that someone is to blame. Developing sounds like something is improving and will get there, so no blame there then, just sadness that we aren't there quite yet.

So, is Chad, say, a developing nation or an under-developed one? Or Congo? Or Kenya? of Mali? Or Peru? Or Somalia? Or Oman?

It's all in the words isn't it?

My money is on under-developed, how about you?