I'd suggest having a closer look at the PDF I linked. As it says in the title, it is a synthesis of reviews.
As I'm sure you know, a review article summarizes recent peer-reviewed, published literature on a topic. For a topic like UBIs, many such reviews are published, and this paper tries to synthesize all of their resuts.
So, they didn't "conduct studies" in this research. They are summarizing the results of the 22 studies that can be found on page 21, the References section.
This paper does the following: "First, it provides an overview of the reviews. Then it synthesizes the basis of evidence (e.g., experiments, policies, and programs) that has been used to arrive at conclusions about UBI as well as the types of outcomes that
have been of interest to researchers and the evidence that exists for these outcomes. The final section highlights gaps in the current state of the evidence and where future research is required."
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@hunkyscotsman @whalecoiner
Such papers are open to criticism on two fronts:
1. The (accurate) summaries of the research done do not actually support the conclusions of the paper
2. The References considered are either misrepresented, or are missing critical research that would support a different conclusion.
Which of these critiques are you making?
/end