Japan has a population of 130 million. It is the largest (by population) non-western developed nation. Edit: It is also the second-largest developed nation in the world.
China is not considered a developed nation? Dang. The things you learn.
(sure, if you look at average well-being including all the people not living in urban areas and average per-capita economic statistics and other similar things, it doesn't look like a major developed power at all... but China has launched manned space missions, has massive high-tech cities, has some pretty darn good scientific projects, and the parts that aren't backwater farms look pretty damn first-world apart from all that oppression-from-the-state business)
At any rate, going by all that's happening over there and all they're doing, I would've expected them to be one by now.
Yes, China included developed and not-yet-developed areas. An interesting question would be how many people live in the developed parts of China -- I'd guess that's in the same ballpark as Japan.
There's a lot of background mess in our mental pictures of the world. We try and be accurate on important issues, but a whole lot of the less important stuff we pick up from the media, the movies, and random impressions. And once these impressions are in our mental pictures, they just don't go away - until we find a fact that causes us to say "huh", and reassess.
Here are three facts that have caused that "huh" in me, recently, and completely rearranged minor parts of my mental map. I'm sharing them here, because that experience is a valuable one.