If quantitative easing (QE) floods the financial system with money by having the Fed buy large quantities of Treasury bonds and mortgage-backed securities, quantitative tightening (QT) is exactly the reverse process: shrinking the Fed's balance sheet by reducing those same holdings. Rather than actively selling bonds outright into the market — which could be disruptive and hard to control — the Fed has generally preferred a gentler method called "runoff": simply allowing bonds to mature naturally on their own schedule and not reinvesting the proceeds into new purchases, letting total holdings shrink passively over time rather than through large, deliberate sales.
This passive approach is a big part of why QT tends to be a slower, quieter process than QE. QE typically involves large, headline-generating purchase announcements with an immediate, visible market effect; QT's runoff mechanism instead unfolds gradually, month by month, as bonds simply mature according to their own pre-set schedules — a structurally less dramatic process, even though the cumulative effect over time can still be substantial.
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