Worldwide, how many of them are still alive?
According to this website:
the area of the world with the highest average lifespan is Okinawa in Japan. The website says:
> Okinawa also has an unusually high concentration of people
> 100 years or older. There are currently about 400 centenarians
> in Okinawa, or 34 for every 100,000 people. The equivalent
> figure for the United States is about 10 in 100,000.
Now, the U.S. has a longer average lifespan than most countries in the world, but there are ten or twenty countries with longer average life spans. So if about 1 person in 10,000 in the U.S. is over 100, I suspect that the worldwide average is somewhere between 1 in 20,000 and 1 in 60,000. There are more than 6 billion people in the world, so I suspect that there are at least 100,000 centenarians in the world and perhaps as many of 300,000. Someone born in the 19th century could be as young as 101, so those numbers aren’t far off as an estimate of the number of people born in the 19th century. I would guess that there are somewhere between 100,000 and 300,000 people born in the 19th century. It would probably take you several hours of searching databases to get a more precise estimate.
That’s the best I can do. Page 29 is most relavent. And it’s from Nov 2001 so it’s recent.