Consider the difficulty of using empirical evidence to isolate the factors that contributed to the "Reagan Boom". Most conservatives would say that it was Reagan's "tax cuts". But he raised taxes as well, so perhaps the boom was due to tax increases (and I'm pretty sure I've heard progressive-types claim this). Or maybe it was the fact that Volcker raised interest rates and stopped inflation, giving businessmen the confidence to plan and invest again. Maybe it was the psychological boost that people got from Reagan's sunny optimism. Maybe it was technological factors: the computer industry was just taking off in the early 80's with home computers, Microsoft, and the rudimentary Internet, driving down costs of doing business enough to give companies extra cost savings that they could then invest. Government spending increased at a high rate during Reagan's tenure; maybe that provided the boost the economy needed.
There are a myriad of others, I'm sure. But suppose one found himself in government power, and wanted to replicate Reagan's "success". Which policies should he enact? The empiricist schools would be unable to inform the government official, because they cannot study human behavior in a vaccuum. Putting someone in a room and studying his actions and reactions cannot reliably predict what that person would do once back out on the street. There is no empirical data that could be collected on human behavior that could reliably predict what effects policies would have. The same policy at one point in time might have positive effects, while at a different point in time produce highly negative effects, because human behavior is not controllable or even, really predictable, because, as Mises said, people act according to what they perceive as their best interests. And since human perception is based partly on human emotion, there is no predictable outcome for human action in any circumstance.