You can't rely on voluntary donations to produce a stable income. A charity doing this would have to vary the amount paid out based on receipts. In hard times

You can't rely on voluntary donations to produce a stable income. A charity doing this would have to vary the amount paid out based on receipts. In hard times, donations and payments will reduce. This will reduce the effectiveness of a UBI in smoothing out recessions. It will also suffer a death spiral because every donor will know how much every recipient gets. If I put in 500 each month and get 200, then I'm going to look for a better place to put my donation. Not because the 200 is a bad RoI for me, but because 200 seems like such a pointless sum for everyone to be getting. I'd rather have that money funding cancer research or more pertinently, I'd rather give all 500 of it to people who need it. Everyone will have their thresholds for what seems "worth it". The lower the payment gets, the fewer donors there will be, and the proportion of the income used for admin will rise.