The right answer to this is not a number, but rather a feedback loop that converges on the right number. When everyone is laid off without production of goods slowing down, the result is deflation; when everyone gets too much money relative to production of goods, the result is inflation. So that means you can use the CPI inflation as a feedback variable, and adjust the UBI amount until the CPI is stable.
I'm all for using a UBI to stabilize inflation (it's way better than giving the money to rich people like we do today), I don't think you got the sizes of things correctly.
Any UBI that avoids people getting poor will have to come mainly form taxes, and will mostly not make any bit of inflation.
Why would it come from taxes, rather than simply from being printed?
The typical answer is "printing money causes inflation", but in the context of this feedback loop, it only causes exactly as much inflation as is required to cancel out the deflation caused by automation-induced layoffs and productivity increases. That's the magic of feedback.
But if it's because the resulting UBI would still be insufficient for welfare, we could also use taxes to fund a secondary "revenue-neutral" layer of UBI that taxes the rich and redistributes to everybody, but probably it makes sense to go in slower steps, seeing what level the primary UBI stabilizes at and then adding a secondary tax-funded one if the primary one isn't sufficient for both welfare and sustaining economic demand.
(The secondary UBI would probably still be somewhat inflationary, even though it's funded by taxes, just because poor people spend more of their money on things that are highly-weighted in the CPI, but the feedback loop will balance that out).
Ideally, the funding for it would on net come from the substantial economic boost created by UBI. More startups, more innovation, more job mobility, higher salaries (because people have more options), more education and training and skilled labor (because people have more ability to not work)...
Indeed. I think one underappreciated economic boost would just be the greater economies of scale that so many production lines will be able to operate at when everyone can afford to buy their output!
