Inflation Study Guide

📖 Core Concepts Inflation – a persistent rise in the overall price level; reduces purchasing power of money. Deflation – a sustained decline in the general price level. Inflation Rate – annual % change in a price index: \(\displaystyle \text{Inflation rate}= \frac{Pt-P{t-1}}{P{t-1}}\times100\%\). Purchasing Power – amount of goods/services a unit of currency can buy; falls when prices rise. Price Index – weighted basket of goods/services used to track price changes (CPI, PPI, GDP deflator, etc.). Core Inflation – CPI‑type measure that excludes food & energy to filter out volatile items. Quantity Theory of Money – inflation occurs when money grows faster than real output: \(M\cdot V = P\cdot Q\). 📌 Must Remember Hyperinflation: > 50 % per month. Disinflation: falling inflation rate while price level still ↑. Stagflation: high inflation + low growth + high unemployment. NAIRU: unemployment rate at which inflation is stable; below it → accelerating inflation. Real interest rate ≈ nominal rate – inflation rate (\(R = N - I\) for small rates). Central banks typically target ≈ 2 % annual inflation. Phillips Curve: short‑run inverse link between unemployment and inflation; trade‑off weakens under credible policy. 🔄 Key Processes Calculating Inflation Rate Obtain price index values \(P{t-1}\) (previous period) and \(Pt\) (current). Plug into \(\frac{Pt-P{t-1}}{P{t-1}}\times100\%\). Monetary‑Policy Transmission Central bank changes policy rate → alters borrowing costs → shifts aggregate demand → moves inflation toward target. Credibility amplifies effect by anchoring expectations. Adaptive Expectations Update \(Et = \lambda \times \text{actual}{t-1} + (1-\lambda) \times E{t-1}\) (weighted average of past inflation and prior expectations). Rational Expectations Formation Agents use all available information (including policy stance) → expected inflation ≈ actual future inflation; no systematic bias. 🔍 Key Comparisons Demand‑Pull vs. Cost‑Push Inflation Demand‑Pull: ↑aggregate demand > supply → firms raise prices. Cost‑Push: ↑input costs (e.g., oil) or supply shocks → firms pass higher costs to consumers. Adaptive vs. Rational Expectations Adaptive: relies on past inflation; slower to adjust. Rational: incorporates full information; adjusts instantly to policy changes. CPI vs. Core CPI CPI: includes all items, volatile food & energy. Core CPI: excludes food & energy → smoother trend of underlying inflation. Hyperinflation vs. Moderate Inflation Hyperinflation: > 50 %/month, destabilizes currency. Moderate: 1‑3 %/yr, can aid labor‑market adjustments. ⚠️ Common Misunderstandings “All inflation is bad.” – Moderate inflation can lower unemployment (via wage‑stickiness) and give central banks policy room. “Higher money supply always raises prices instantly.” – In the short run, velocity and output may change; long‑run relationship is stronger (Monetarist view). “Core inflation ignores important price changes.” – It purposefully omits volatile items to reveal trend, not to deny their impact. “Deflation is simply low inflation.” – Deflation is a negative price growth, often accompanied by a debt‑deflation spiral. 🧠 Mental Models / Intuition “Money‑Growth = Price‑Growth” – Think of the economy as a bathtub: adding water (money) faster than the tub expands (output) overflows as higher prices. “Expectations as self‑fulfilling prophecy.” – If everyone expects higher prices, they spend sooner, pushing demand up now → price rise. “NAIRU as a “sweet spot”. – Visualize a horizontal line (NAIRU) on a graph of unemployment vs. inflation; the economy “wants” to hover near it. 🚩 Exceptions & Edge Cases Velocity not constant – In crises, V can drop sharply, weakening the direct link between money growth and inflation. Supply‑side shocks with low demand – Cost‑push can raise prices even when demand is weak (e.g., oil shock in a recession). Currency devaluation – Can cause imported inflation even if domestic money growth is modest. 📍 When to Use Which Choose CPI when you need a broad measure of consumer‑price changes for policy reporting. Use Core CPI to assess underlying inflation trends, stripping out food/energy volatility. Apply the Equation of Exchange (\(M V = P Q\)) for long‑run analysis of monetary influence on price level. Rely on Adaptive Expectations in simple macro models where agents have limited information. Adopt Rational Expectations in New‑Keynesian frameworks that stress policy credibility. 👀 Patterns to Recognize “Rising PPI → Later CPI rise.” – Producer‑price changes often lead consumer‑price changes. “Unemployment below NAIRU → Inflation acceleration.” “Policy‑rate cuts + credible central bank → immediate drop in long‑term inflation expectations.” “Sharp supply shock + weak demand → stagflation pattern (high inflation & stagnant growth). 🗂️ Exam Traps Choosing “inflation = money supply growth” without mentioning output or velocity – the equation is \(M V = P Q\), not just \(M\). Confusing disinflation with deflation – disinflation is a slowing of inflation, not a price decline. Picking “CPI” as the “most stable” index – core CPI is more stable for trend analysis. Assuming hyperinflation is always caused by excessive money printing – political collapse, loss of confidence, and fiscal deficits often combine. Mixing up “inflation tax” with actual fiscal taxes – the “inflation tax” is the erosion of real money holdings, not a statutory tax.