Four Reasons Keynesians Keep Getting It Wrong

From Allan Meltzer, at Wall Street Journal:

Those who heaped high praise on Keynesian policies have grown silent as government spending has failed to bring an economic recovery. Except for a few diehards who want still more government spending, and those who make the unverifiable claim that the economy would have collapsed without it, most now recognize that more than a trillion dollars of spending by the Bush and Obama administrations has left the economy in a slump and unemployment hovering above 9%.

Why is the economic response to increased government spending so different from the response predicted by Keynesian models? What is missing from the models that makes their forecasts so inaccurate? Those should be the questions asked by both proponents and opponents of more government spending. Allow me to suggest four major omissions from Keynesian models...

RTWT.