Simulated Dendrochronology of US Immigration 1790-2016
web.northeastern.edu
web.northeastern.edu
I'm not sure I can read all the story-arcs of change over time on this un-adorned. I think the photo of a huge redwood trunk with significant events in the human timeline overlaid might be in my mind here: left could be legal changes affecting immigration, right could be world events stimulating immigration eg the boom and bust and famine cycle.
[1] https://en.m.wikipedia.org/wiki/Act_Prohibiting_Importation_...
> Tree rings that are nearly circular indicate that population growth due to immigration was much less significant than that due to natural-born persons.
And I missed that census data is the source. Because at 100% in Firefox, the relevant paragraph ends:
> The data was queried from IPUMS-USA and consists of millions of samples of questionnaires from U.S.
At 110%, I see that it's actually:
> The data was queried from IPUMS-USA and consists of millions of samples of questionnaires from U.S. Censuses.
So yeah, I guess that census data didn't include slaves.
I’d guess a change in visa rules, with possibly some pent-up demand.