[scythe]

Early advocates (e.g. Friedman) for UBI (and also NIT) often focused on broader distributional outcomes for society and the economy as a whole. One is the reduction of the "welfare cliff". Another is the increase in relative spending power of the lower class as a group, which could lead to growth in businesses that serve these cohorts. Neither of these effects is assessed at all by RCTs that look at a small population of individuals for a period of less than a decade, because they are effects that occur over a long time and among a necessarily large (millions) group of people.

There is a sort of unstated assumption among some social policy critics that goes, roughly, "we can test most policy effects that matter with well-designed trials". People believe this less because there is any evidence for it and more because modern experimental science is impressive and successful in many ways and so therefore must have the answer to any question. However, many policy questions remain "wicked" and outside of a reasonable experimental domain.