I'll assume you meant from market creation, until the start of 2040. But you didn't specify that anywhere, so what do we do with these?

Mongolia

"In 2010, the child-oriented payments were replaced with the new Human Development Fund (HDF) that was financed from mining dividends to provide a universal basic income that was paid monthly to every citizen. Mongolians monthly received MNT 21 thousand between 2010 and 2012 through the HDF."

Looks like this was around 17-18 USD at the time.

Can't find wages from that time, looks like minimum wage was sub 190k.

If these are median wages, then median was ~ 400k.

So the UBI was 5% of the median wage?

Iran

"The government started monthly deposits of cash into individual family accounts amounting to 29% of the median household income and 6.5% of the GDP. This amounts to about $1.50 extra income per person per day."

A bit more data https://www.unicef.org/media/70456/file/IRN-case-study-2020.pdf

"The cash transfer reached almost universal coverage in 2011, with 73 million Iranians receiving cash benefits, costing the Government IRR 3,300 billion every month."

This looks more substantial than Mongolia case, and also ~25x more people.

Seems to me:

Before 2040 ✓

Any length of time ✓

Nationwide ✓

Formal legislation ✓

Would it be a good idea to set some minimum amount as what counts as UBI? According to wiki there is full basic income and partial basic income. Alaska has a form of UBI, but its only a few % of the avg annual income. I'm saying this because if a country decides to give everyone $1, once, it would satisfy all your conditions.

@light I agree, these already satosfy the market. Some sort of condition should be added to this market to make it more worthwhile. Something alongside UBI being the previous minimum wage or something like that.

@light hmmmmmm, very good point. That's my bad I probably should've looked into it more before I clarified the criteria. I think it wouldn't be much fun to just resolve the market now since this wasn't rly what I intended anyway. I will redefine the criteria to be a "full UBI", which I believe is one that covers all of the basic living expenses of an average person (in case "full UBI" means something different just use the definition I gave here).

@VictorLi Good clarification. I would suggest adding the criteria of it being a "full UBI" to the description of this market and, I assume to all the other markets regarding UBI that you have made, as this does alter the odds in my opinion.

@ScipioFabius I added the updated descriptions to all of my markets, but note that the 2030 US one is slightly different

What would be your criteria for resolution? How big should the UBI be?

@ScipioFabius any system of universal basic income being installed in any country for any length of time (though it has to be nationwide and a formal legislation instead of regional trials) would be enough for this to resolve YES.