So the persistence of unemployment is being blamed on aggregate demand failure by administration officials such as Christine Romer and Lawrence Summers. But my question is actually serious. I honestly don't know what aggregate demand really is let alone how we can get an economically meaningful measurement of it (whatever "it" is supposed to be). My thought process goes more in the direction of the way J. B. Say responded to Thomas Malthus when discussing a general glut, or W. H. Hutt's response to Keynes in The Theory of Idle Resources. Aren't economic patterns really just a by-product of relative price adjustments?
Why is this mainline of economic thinking response so out of favor with the current mainstream of economic theory and policy? In short, why has the argument that while there may be macroeconomic problems, there are only microeconomic explanations and solutions fallen on deaf ears among so many economists and economic students?