How Did Economists Get It So Wrong? - NYTimes.com
Economists got it wrong by:
Believing their own bullshit. Economy, as a science, is really a belief system. These mere mortals think that they are masters of the universe.
Politicizing their beliefs. Economists used the political tactic "if you repeat a lie (or a belief) often enough, people will start to believe it.
They forgot the definition of insanity - doing something repeatedly and expecting the results to change. Every strong Republican/supply-side/trickle-down administration has plunged the country into recession. Standing this ground on idealogical feet makes no sense, except to a complicit media and a public willing to accept lies.