Norah - She/They

That’s an entirely different thing than “per unit of time”. It’s a valid question, turns out there isn’t an answer, but some very basic searching linked me to the original map as released: http://cf.datawrapper.de/dduui/2/

To your edit, sure, there are diaspora maps for timeframes. Those are called immigration/emigration maps, because the acts of which grow or shrink a diaspora.

Yes, exactly, hence “per all time, that are still alive” because it’s measuring the current number of American-born residents of each country, compared to the residents from said country in America.

Read it again. There’s not a “per when” because it’s measuring the Diasporas, which would just be “per all time, that are still alive”

It is literally written, right there, in the subheading:

Foreign Diaspora in the United States Less US Diaspora in Foreign Country, as a Share of Foreign Country Population