M2 Money Supply vs CPI
Monetarists argue money-supply growth eventually drives inflation. The 2020–22 episode — M2 surging, then CPI surging — is the clearest test in a generation.
- M2
- CPI
The quantity theory of money holds that, in the long run, the inflation rate roughly equals money growth minus real-output growth. That relationship broke down in the late 2010s — M2 grew steadily while inflation stayed below the Fed's 2% target — and many economists concluded monetarism was dead.
Then 2020 happened. M2 grew 25% year-over-year, the fastest ever recorded. CPI followed two years later, peaking at 9.1% in June 2022. M2 contracted in 2023 — a rare event — and CPI cooled sharply afterward. Whether that was coincidence or causation is actively debated, but the episode resurrected interest in money-supply analysis that had been out of fashion for a decade.
Comparing M2 and CPI year-over-year growth directly gives the cleanest view of the relationship. Monetarists look for M2 acceleration as a leading signal for inflation roughly 12–24 months ahead.
Frequently asked questions
Does money supply growth cause inflation?
The quantity theory of money holds that, in the long run, inflation roughly equals money growth minus real-output growth. The relationship broke down in the late 2010s — M2 grew while inflation stayed below 2% — but the 2020–22 episode, where M2 surged 25% and CPI peaked at 9.1% two years later, revived the debate. Whether it was causation or coincidence remains contested.
How far ahead does M2 lead inflation?
Monetarists watch M2 acceleration as a leading signal for inflation roughly 12–24 months ahead. In the most recent cycle, record M2 growth in 2020 preceded the CPI peak in mid-2022, and M2's rare contraction in 2023 was followed by sharply cooling inflation — though the lag and reliability of this relationship are actively debated.
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