I don't know if there's a threshold per se, but the X-axis on the graph you cited is demarcated as 10k per line. 250 dollars a year is about 1/40th of each unit on the X-axis.

And that graph seems to apply to people all over the world, I don't see why this Kenyan village would be any different.

The fertility reductions really only seem to matter once you get to 10k or 20k of annual income a year. I agree that if you gave 10k a year strings unattached to every person in that community, fertility might drop.

However, by injecting that much capital into a poverty stricken area, fertility might actually increase, as they would be the most prosperous group by far in the area. Also, there would almost certainly be huge unintended consequences, such as massive inflation and the increase in deprivation of people not receiving the money.

Yes, you make some sound points here for sure. What is your position on the concept of universal basic income, setting aside beta tests for now.

And what do you think it's viable, what would it take to make it viable. Maybe consider a few scenarios say how it might work (or not work) in different parts of the world, including both developing and developed.

I don't know enough about UBI to say anything for sure.

I know that either UBI will have to be so slow that it'll be useless for those in a first world country (like 250 dollars a year) or else we'll have to have far stricter immigration controls than ever - a UBI for first world standards would be unimaginable luxury for those living in third world conditions.

Fundamentally I think it comes down to population control. A geometrically increasing population is simply not sustainable for any long enough period of time. My personal opinion is that if UBI could be linked to contraception (you only receive UBI if you're not allowed to have children while on UBI or take care of children with your UBI funds) then that could work.