Japanese are getting taller and taller.
I always notice this at the start of an academic year when I look out at the freshmen in my class. When I first came to Japan, I was usually the tallest person in the room. On the bus, in an elevator, or on the train, I had a clear view over everyone's head. Then about ten years or so ago, that view started to get obstructed by foreheads and tops of heads. Now, there are many who are as tall as, or taller than, me and quite a few who tower over me.
I asked my son what he thought about it. He's the tallest kid out of some 120 in his grade. This is clearly thanks to my wife's good genes, but we often joke that his height is thanks to Nattō Power.
"When I came to Japan, everyone was about this tall," I said, pointing to my shoulder. "Now everyone's this big. In only twenty years, they've gone from here to here. Do you think it's nattō that's making everyone get so tall?"
"No," my son answered flatly. "Everyone grew so that they could put distance between their noses and your stinky bottom."
"You know, you might be right."