Quantitative Easing: AP Macroeconomics Study Guide

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Where QE Fits in the Course

Quantitative easing sits at the edge of the AP Macroeconomics syllabus: the exam concentrates on conventional open market operations, but QE is the natural extension of that material and it appears regularly in stimulus questions and in classroom discussion of the post-2008 period. The connection to make is that QE is still an open market operation — the central bank buys securities and pays for them by crediting bank reserves — but it differs in two ways the course cares about. It targets longer-maturity assets rather than short-term Treasury bills, and it is used specifically when the short-term policy rate can no longer be cut. Understanding that link is usually enough for exam purposes.

The Zero Lower Bound on the Money Market Graph

On the standard money market diagram, an expansionary open market purchase shifts the vertical money supply line to the right and the nominal interest rate falls. The complication QE addresses is that the nominal rate cannot fall meaningfully below zero, because holding currency always pays zero. Once the equilibrium sits at that floor, further rightward shifts in the money supply do not lower the rate any further — the money demand curve is effectively flat there, a situation older textbooks describe as a liquidity trap. That is the graphical reason a central bank reaches for tools that operate on long-term rates and on expectations rather than on the overnight rate.

Linking to AD-AS and to Inflation

The intended chain is the same one you already draw for conventional easing: lower long-term interest rates raise interest-sensitive investment and consumption, which shifts aggregate demand right, raising real output and the price level in the short run. Where QE questions get interesting is in the follow-up. If the economy is in deep recession with substantial spare capacity, the short-run aggregate supply curve is relatively flat over that range, so most of the effect shows up as higher output rather than higher prices. That reasoning is the standard explanation offered for why the very large balance sheet expansion after 2008 was not accompanied by high inflation, and it is a strong point to make in a free-response answer.

Key Terms to Know