One big problem i see with all of these tests is that they are temporary. The people receiving the money know they're only going to be getting it for a year and, therefore, these tests don't reflect how people would live and act if they knew they would be receiving this money for a lifetime. However, there is already at least one such project in existence (and probably a lot more that I don't know about) - the Alaska Permanent Fund Corporation. This program has been providing income for Alaskan residents since 1982. However, it is much less than in this test (~$300-$2000 per year) and Alaskan residents are already receiving it so you can't go back and study how people's lives change when they first started receiving it.
Now, aside from how the studies are conducted, the two biggest issues I have with UBI (universal basic income):
- currently unemployment in the US is very low, so it is unclear if this "great job loss due to computers replacing people in the workplace" will ever materialize. People have been wringing their hands about this very issue for at least a hundred years. Is this time different? Maybe, maybe not... I'll believe it when i see it.
- it is extremely expensive. Let's say you give 200 million people n the US each $20,000 per year. You're talking about $4 trillion dollars of goods and services that someone has to generate to fund this program...
For the foreseeable future, in my opinion, UBI just seems the me to be a retelling of the utopian dream...