For essentially three reasons: - ethics. Example: is democracy good for economic growth? Of course one could randomly engineer coups in some countries but that

For essentially three reasons: - ethics. Example: is democracy good for economic growth? Of course one could randomly engineer coups in some countries but that's probably not appropriate. - cost. Example: how much do people change their labor force participation when taxes change by 1%? where a RCT would be "let's give a _lot_ of money to people" and see what happens. - situation where it is not appropriate. Example: why did Europe rise to prominence (aka the great divergence)? There is not much to randomize here. Note that RCTs have shortcomings anyway (see for instance [0]). [0] https://www.nber.org/papers/w22595 https://www.nber.org/papers/w22595