There is a lack of research into the optimal amount of guaranteed income.

"...for a given budget constraint, each dollar disbursed on a guaranteed income is one not spent on other necessary programs, so it is reasonable to ask about cost-effectiveness: what is the optimal benefit amount from a cost-benefit perspective? At what point ($3600/year? $7200/year? $12,000/year?) do decreasing marginal impacts per dollar disbursed suggest that the money may be better spent elsewhere? Here again, evidence is limited as there are few studies that directly compare the impacts of different transfer amounts."

empirical