[swampangel]

The linked report makes the distinction a little clearer:

> For the most part, we focus on the labor supply of poorer workers, who are more likely to reduce their labor supply as a result of a modest increase in unearned income. Our results do not indicate a negative labor supply effect for either hours worked or the probability of participation in market work, either for all workers or those in the bottom 40% of the income distribution. We do find a negative labor supply effect for workers 20-29 years old for their hours worked.

[notahacker]

The linked report is also more comprehensive than the summary, including the points that: (i) the next Iranian government and Iranian press strongly believe that it did cause massive reductions in labour supply in certain suggestions including citing a paper claiming a loss of 500,000-700,000 agricultural workers[2] (ii) the context of the poorer people not dropping out of work was a period of enormous inflation (caused in part by US sanctions) and the removal of enormous food and fuel subsidies which the program replaced and (iii) this measures very short term impacts (prior to the program launch and within the first three months): against the backdrop of rising prices and brand new US sanctions it's perhaps particularly unlikely that many poorer workers would rush to quite their jobs, even if it were to produce such an effect in the longer term in times of greater economic security (iv) it's actually specifically focusing whether people were more likely to quit their jobs than people who didn't get the subsidy for the first three months due to paperwork problems rather than whether employment didn't fall overall; the paper correctly points out that in an economy with wide access to cheap credit (not Iran) the orthodox economic view would actually expect those receiving subsidies now and those expecting to receive them asap to respond by reducing willingness to supply labour by similar amounts (v) there was a perfectly good reason for them doing the study that way because Iranian labour force trends are all over the place

TLDR: the actual study doesn't tell us very much through no fault of the authors, because a lot of other shocks were happening to the economy at the time. Which is a shame, because it was a huge new program in a middle income country that didn't involve outside capital, which would have made it much better evidence of a UBI's expected effects than most studies carried out.

[2]having read that paper as well, it doesn't appear to be a claim with empirical support