Between 2021 and 2023 the world experienced its worst inflation surge in four decades: US CPI inflation peaked at 9.1% in June 2022, the Eurozone hit 10.6%, and the UK reached 11.1%. For students, this episode is a gift — it turned every textbook theory of inflation into live news, and examiners have been mining it for questions ever since. This guide covers the classic theory (demand-pull, cost-push, monetary), then digs into what frontier research says actually happened.
Defining Inflation Properly
Inflation is a sustained increase in the general price level, typically measured by the Consumer Price Index (CPI) or the GDP deflator. Two definitional traps cost exam marks:
- A one-off price jump is not inflation unless it feeds into a continuing process.
- Disinflation (inflation falling from 9% to 3%) is not deflation (prices actually falling). Prices are still rising during disinflation — just more slowly.
Demand-Pull Inflation
Demand-pull inflation occurs when aggregate demand grows faster than the economy’s productive capacity — “too much money chasing too few goods.” On the AD/AS diagram, the AD curve shifts right along an upward-sloping (or vertical, at full employment) SRAS curve, raising the price level.
Causes: expansionary fiscal policy (tax cuts, stimulus payments), loose monetary policy (low interest rates, quantitative easing), consumer confidence booms, export surges, and wealth effects from rising asset prices.
The 2021 US experience is now the canonical example: the $1.9 trillion American Rescue Plan (March 2021) landed on top of $2.2 trillion (CARES Act) and $900 billion of earlier stimulus, while households were sitting on roughly $2 trillion of excess pandemic savings. Demand for goods exploded before supply chains could recover.
Cost-Push Inflation
Cost-push inflation occurs when production costs rise, shifting the SRAS curve left: prices rise while output falls — the dreaded combination of stagnation and inflation known as stagflation.
Causes: energy and commodity price shocks, supply chain disruption, wage growth exceeding productivity, currency depreciation (raising import prices), and higher indirect taxes.
The 2022 episode delivered a textbook supply shock: Russia’s invasion of Ukraine in February 2022 sent European natural gas prices up more than 10-fold at the peak, Brent crude above $120, and global food prices (wheat, sunflower oil, fertiliser) to record highs. Shipping costs had already exploded — the Freightos global container index rose from around $1,500 pre-pandemic to over $11,000 in September 2021.
The Monetarist View
“Inflation is always and everywhere a monetary phenomenon.” — Milton Friedman (1963)
Monetarists argue sustained inflation requires sustained money supply growth: MV = PQ (the quantity theory). If velocity (V) and output (Q) are stable, money growth (M) translates into price growth (P). The M2 money supply in the US grew over 40% between February 2020 and early 2022 — the fastest expansion in modern history — and monetarist economists point to this as the deep cause the mainstream initially underweighted. Critics respond that velocity collapsed during the pandemic and that the money-inflation link had been weak for three decades before 2020. The debate is a rich source of A-Level evaluation marks.
What Does the Research Say Actually Happened in 2021–2024?
This is where you can separate yourself from every other exam candidate. Three landmark studies decomposed the surge:
1. Bernanke & Blanchard (2023): supply first, labour market later
Former Fed Chair Ben Bernanke and Olivier Blanchard built a model of the US inflation surge and concluded that the initial burst (2021–early 2022) was driven overwhelmingly by supply-side shocks — energy prices, supply chain bottlenecks, and sectoral demand shifts (the great rotation from services to goods during lockdowns). However, they warned that as those shocks faded, the tight labour market (US job vacancies peaked near 12 million against 6 million unemployed) became the dominant driver of remaining inflation — making the “last mile” back to 2% the hardest.
2. Shapiro (2022): a roughly even split
Adam Shapiro of the San Francisco Fed decomposed PCE inflation into supply-driven and demand-driven components by examining whether prices and quantities moved in the same direction (demand shock) or opposite directions (supply shock) category by category. His finding: supply factors explained roughly half of the 2021–22 surge, demand about a third, with the remainder ambiguous. This elegant identification strategy is worth understanding — it is essentially applied AD/AS analysis.
3. Ball, Leigh & Mishra (2022, IMF): headline shocks pass through
This influential IMF paper showed that most of the rise in US core inflation came from the pass-through of headline shocks (energy, food) into core prices, plus labour market tightness measured by the vacancy-to-unemployment ratio. Their sobering conclusion at the time: returning inflation to target would likely require a meaningfully cooler labour market.
The surprise ending: immaculate disinflation?
Here is the twist worth an evaluation paragraph: inflation fell from 9% to near 3% in the US by late 2023 without a recession and without mass unemployment — contradicting predictions (based on Phillips curve sacrifice ratios) that disinflation would require years of high unemployment. Supply chains healed, energy prices retreated, labour supply recovered (including through immigration), and inflation expectations stayed anchored. The episode has forced a rethink of how costly disinflation must be when the initial shock is largely supply-driven and central bank credibility is intact.
Famous Case Studies Every Student Should Know
Weimar Germany (1923)
The classic hyperinflation: prices doubling every few days, workers paid twice daily, banknotes used as wallpaper. Root cause: the government printed money to finance reparations and support striking workers in the occupied Ruhr. It ended almost overnight with the Rentenmark and credible fiscal reform — evidence that expectations and credibility, not just money supply mechanics, drive hyperinflation.
Zimbabwe (2007–2009)
Peak monthly inflation estimated at 79.6 billion percent (November 2008). Caused by money-financed deficits amid collapsing output after land reform. Ended by abandoning the Zimbabwe dollar entirely — “dollarization.”
Venezuela (2016–2019)
The major 21st-century hyperinflation: the IMF estimated inflation above 1,000,000% in 2018. A combination of oil revenue collapse, monetised deficits, price controls, and exchange rate collapse. Over 7 million Venezuelans emigrated — a reminder that inflation is not an abstract statistic.
Argentina (2023–2024)
Annual inflation reached 211% in 2023 — the highest in three decades — before the Milei government’s shock-therapy program of fiscal consolidation brought monthly inflation down sharply through 2024, at the cost of a deep initial recession. A live case study in the fiscal theory of inflation and the costs of stabilisation.
Why Moderate Inflation Matters: The Costs
- Erosion of real incomes, hitting fixed-income households hardest — UK real wages fell for 18 consecutive months during 2022–23.
- Menu costs and shoe-leather costs — the classic microeconomic frictions.
- Uncertainty deterring investment and long-term contracts.
- Arbitrary redistribution from savers/lenders to borrowers (unanticipated inflation reduces the real value of debt).
- Fiscal drag — with frozen tax thresholds, inflation quietly pushes workers into higher tax bands.
- International competitiveness loss if domestic inflation outpaces trading partners under fixed exchange rates.
Exam Technique: Structuring the Classic Essay
For “Discuss the causes of the recent rise in inflation” (a near-certain A-Level question in coming years):
- Define inflation; distinguish demand-pull and cost-push with an AD/AS diagram for each.
- Apply to 2021–24: stimulus + excess savings (demand-pull); energy, shipping, war (cost-push); money growth (monetarist).
- Evaluate: use Bernanke–Blanchard and Shapiro to argue causes shifted over time; note the difficulty of decomposition; mention the role of expectations and central bank credibility.
- Conclude with a judgement: initial surge mostly supply, persistence increasingly demand/labour-market driven.
Think Deeper: Exercise Questions
- Research question: Bernanke & Blanchard (2023) argue that supply shocks caused the surge but labour market tightness caused its persistence. If true, what does this imply about whether central banks should respond aggressively to the initial phase of a supply-driven inflation? Read: Bernanke, B. & Blanchard, O. (2023), “What Caused the U.S. Pandemic-Era Inflation?” Brookings/Peterson Institute Working Paper.
- Data exercise: Using Shapiro’s logic, if the price of used cars rises while the quantity sold also rises, is that a demand or supply shock? What if airfares rise while passenger numbers fall? Test yourself on five categories, then compare with Shapiro (2022), “How Much Do Supply and Demand Drive Inflation?” FRBSF Economic Letter.
References
- Bernanke, B. S., & Blanchard, O. (2023). What Caused the U.S. Pandemic-Era Inflation? Peterson Institute for International Economics / Brookings Working Paper.
- Shapiro, A. H. (2022). How Much Do Supply and Demand Drive Inflation? FRBSF Economic Letter, 2022-15.
- Ball, L., Leigh, D., & Mishra, P. (2022). Understanding U.S. Inflation During the COVID Era. Brookings Papers on Economic Activity, Fall 2022.
- Friedman, M. (1963). Inflation: Causes and Consequences. Asia Publishing House.
- Guerrieri, V., Lorenzoni, G., Straub, L., & Werning, I. (2021). Macroeconomic Implications of COVID-19: Can Negative Supply Shocks Cause Demand Shortages? American Economic Review, 112(5).
- Hanke, S. H., & Krus, N. (2013). World Hyperinflations. In The Routledge Handbook of Major Events in Economic History.